How to calculate tax based on 4 decimals?

Question

Magento 2 calculates the price Inc tax based on 2 decimals. I managed to save the price as 4 decimals. This get's stored in the catalog_product_entity_decimal table.

The problem now is that the vat does not get calculated based on the 4 decimals but the 2.

Example:

• Stored price: 41,275200
• vat percentage: 9 %
• expected price inc VAT: 44,989968 (displayed as 44,99)
• actual price displayed 45,00 (41,28 x 1,09 = 44,9952)

How can I fix this, I want the calculations based on all the decimals (4 in my case), but still want to display prices with 2 decimals?

Answer 1

Create a Custom Module:

1. Create di.xml file under {Vendor}/{CustomModule}/etc folder:

   <?xml version="1.0"?>
   <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
   xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
       <type name="Magento\Tax\Model\Calculation">
           <arguments>
               <argument name="priceCurrency" xsi:type="object">{Vendor}\{CustomModule}\Model\PriceCurrency</argument>
           </arguments>
       </type>
   </config>`
   

2. Create PriceCurrency Model Class File under {Vendor}/{CustomModule}/Model folder:

class PriceCurrency extends \Magento\Directory\Model\PriceCurrency
{

    const DEFAULT_PRECISION = 4;

    public function round($price)
    {
        return round($price, self::DEFAULT_PRECISION);
    }

    public function convertAndRound($amount, $scope = null, $currency = null, $precision = self::DEFAULT_PRECISION)
    {
        return parent::convertAndRound($amount, $scope, $currency, $precision);
    }
}