Magento 2: Custom tax not beign sent to paypal

Question

I am adding custom tax based on a particular shipping and payment method using the following plugin:

use Magento\Customer\Api\Data\AddressInterfaceFactory as CustomerAddressFactory;
use Magento\Customer\Api\Data\RegionInterfaceFactory as CustomerAddressRegionFactory;
use Magento\Quote\Api\Data\ShippingAssignmentInterface;
use Magento\Quote\Model\Quote\Address;

class Tax extends \Magento\Tax\Model\Sales\Total\Quote\Tax
{
  /**
    * Class constructor
    *
    * @param \Magento\Tax\Model\Config $taxConfig
    * @param \Magento\Tax\Api\TaxCalculationInterface $taxCalculationService
    * @param \Magento\Tax\Api\Data\QuoteDetailsInterfaceFactory $quoteDetailsDataObjectFactory
    * @param \Magento\Tax\Api\Data\QuoteDetailsItemInterfaceFactory $quoteDetailsItemDataObjectFactory
    * @param \Magento\Tax\Api\Data\TaxClassKeyInterfaceFactory $taxClassKeyDataObjectFactory
    * @param CustomerAddressFactory $customerAddressFactory
    * @param CustomerAddressRegionFactory $customerAddressRegionFactory
    * @param \Magento\Tax\Helper\Data $taxData
    */
    public function __construct(
        \Magento\Tax\Model\Config $taxConfig,
        \Magento\Tax\Api\TaxCalculationInterface $taxCalculationService,
        \Magento\Tax\Api\Data\QuoteDetailsInterfaceFactory $quoteDetailsDataObjectFactory,
        \Magento\Tax\Api\Data\QuoteDetailsItemInterfaceFactory $quoteDetailsItemDataObjectFactory,
        \Magento\Tax\Api\Data\TaxClassKeyInterfaceFactory $taxClassKeyDataObjectFactory,
        CustomerAddressFactory $customerAddressFactory,
        CustomerAddressRegionFactory $customerAddressRegionFactory,
        \Magento\Tax\Model\Calculation $taxCalculation,
        \Magento\Tax\Helper\Data $taxData,
        \Magento\Customer\Model\Session $session,
        \Magento\Customer\Model\Group $group
        ) {
        
        $this->setCode('tax');
        $this->taxCalculation = $taxCalculation;
        $this->session = $session;
        $this->group = $group;

        parent::__construct(
            $taxConfig,
            $taxCalculationService,
            $quoteDetailsDataObjectFactory,
            $quoteDetailsItemDataObjectFactory,
            $taxClassKeyDataObjectFactory,
            $customerAddressFactory,
            $customerAddressRegionFactory,
            $taxData
        );
    }
    
    /**
    * Custom Collect tax totals for quote address
    *
    * @param Quote $quote
    * @param ShippingAssignmentInterface $shippingAssignment
    * @param Address\Total $total
    * @return $this
    */
    public function collect(
        \Magento\Quote\Model\Quote $quote,
        \Magento\Quote\Api\Data\ShippingAssignmentInterface $shippingAssignment,
        \Magento\Quote\Model\Quote\Address\Total $total
    ) {
        parent::collect($quote, $shippingAssignment, $total);

        $taxamount = 0;     
        $customerSession = $this->session;
        $customerGroup = $this->group;
        $customerGroupId = $customerSession->getCustomer()->getGroupId();
        $collection = $customerGroup->load($customerGroupId);
        $customerGroup = $collection->getCustomerGroupCode();
        $shippingAddress = $quote->getShippingAddress();
        $shippingMethod = $shippingAddress->getShippingMethod();

        if($shippingMethod == 'shqpickup1_collect'){
             
            foreach($quote->getAllVisibleItems() as $item) {
                
                // Tax Calculation
                $productTaxClassId = $item->getTaxClassId();

                $request = new \Magento\Framework\DataObject(
                    [
                        'country_id' => 'US',
                        'region_id' =>'43',
                        'postcode' => '10001',
                        'customer_class_id' => '3',
                        'product_class_id' => $productTaxClassId
                    ]
                );
                
                // Calculate tax
                $taxInfo = $this->taxCalculation->getResource()->getRateInfo($request);
                
                // Classify different taxes
                if (count($taxInfo['process']) > 0) {
                    foreach ($taxInfo['process'][0]['rates'] as $key => $rate) {
                        $itemPrice = $item->getQty() * $item->getPrice();
                        if($item->getDiscountAmount() > 0){
                            $itemPrice = ($item->getQty() * $item->getPrice())-$item->getDiscountAmount();
                        }
                        $taxamount += ($itemPrice * $rate['percent']) / 100;
                    }
                }
            }

            // echo 'Tax amount: '.$taxamount;

            if($customerSession->isLoggedIn()){
                // Tax Exempt Customer
                if($customerGroup != 'Tax Exempt Customer'){
                    $total->setTaxAmount($taxamount);
                    $total->setBaseTaxAmount($taxamount);
                    $total->setTotalAmount($this->getCode(),$taxamount);
                    $total->setBaseTotalAmount($this->getCode(),$taxamount);
                }
            }else{              
                $total->setTaxAmount($taxamount);
                $total->setBaseTaxAmount($taxamount);
                $total->setTotalAmount($this->getCode(),$taxamount);
                $total->setBaseTotalAmount($this->getCode(),$taxamount);
            }
        }       

        return $this;
    }

Paypal is not accepting this amount. When I click place order it redirects to the paypal site and after entering the payment it redirects back to the order review page with an error: 'PayPal NVP gateway errors: This transaction couldn't be completed. Please redirect your customer to PayPal'.