How does Shopify calculate tax on discounted orders?

[DazOel]

Hi There,

We are attempting to calculate the tax on an order. We are working with a 15% (South Africa) tax rate.

I am struggling to understand how Shopify is calculating the tax on orders. Please explain the following:

- Order Sale Value = R179,90

- Discount Offered: 10%

- 10% of R179.90 = R17,99

To calculate the discount value (on 17.99) WITHOUT the added 15% tax:

- R17.99 / 1.15 = R15.643478260869

Please explain how Shopify rounds 15.6434782 to 15.63 ????????????????????

R15.63 + 15%(vat) = R17.97 

R15.643478260869 + 15%(vat) = R17.989999999

Please find figures attached.

Thank you, looking forward to the clarification.