UK Tax Calculation Rounding issues

Question

I'm running a Magento 1.9.0.1 build with the 'Tax Calculation Method Based On' setting set to Total but running into the issue of tax and total prices coming out at 1 pence less than it should be. I wondered if someone could help with figuring how to correct this. I have already changed all of the default rounding and precision in various files from 2 to 4.

As an example, Placing an order for 79 of a product with a Unit Price of £2.46 (Ex Tax) the Total (Ex Tax) price is correctly coming out at £194.34. However, the Tax line is coming out at £38.86 and Magento is rounding this from £38.868.

My client would prefer this rounded to £38.87 - since this is how the HMRC and Sage Accounts round these figures. The Order Total would then be £194.34 (Ex Tax) + £38.87 (Tax) = £233.21 (Inc Tax).

Because Magento is currently placing the tax at £38.86 (1p out), the Order Total is also 1p out at £233.20 instead of £233.21 from what Sage Accounts calculates.

This would place a Unit Price inclusive of tax of £2.952 instead of £2.95 (which is also how Sage Accounts would handle this).

We still need the site to display the price as £2.95 in this instance but the customer would need to be charged £233.21 instead of the £233.20 that Magento is currently displaying.

Thank you.

Answer 1

Sorry to hear that you got caught in Magento's age-old issue.

Firstly, check your admin configuration settings are similar to this official link

If this does not resolve the issue, you need to gracefully override the Mage_Core_Model_Store class and change the following method to :

public function roundPrice($price)
{
   return round($price, 4);
}

Remember, this might cause rounding issue on PayPal, but I have not come across any issue with PayPal or AmazonPay after the override.