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How do I get to this same totals?

How do I get to this same totals?

I'm trying to understand how Magento handles the order totals and trying to replicate the same behaviour for a Magento 2 Module. 


This is one of the most weird cases or as we call it, the "100 Coffees Problem". 

The price of each coffee (without VAT) is 0,49€. 

Each coffee has a VAT of 23% applied. 


If we have 10 rows of 10 coffees each, we get this totals: 

Subtotal: 49,00 €

Tax: 11,30 € 

Grand Total: 60,30 €


But if we have for example 1 row of 100 coffees, we have the following totals: 

Subtotal: 49,00 €
Tax: 11,27 € 

Grand Total: 60,27 €


I know this is a corner case and that the Grand Totals will be wrong, but how does it get to 11,30€ in taxes? 



Also, another case that we found during our module development, is for example: 

Three products of 10,65€ (No VAT) + 23% VAT

One product of 10,20€ (No VAT) + 23% VAT


And the end totals are: 

Subtotal: 42,16 € 

Tax: 9,70 € 

Grand Total: 51,85 €


How do can I do my cals right so that I get the same totals?