Please try ths:
Put some order in cart reaching a total cart value of 100.00
Go to Administrator > Setup > Tax Mode and set to: Enabled
Set Tax Rate: 10
Then test these two cases
1 - Apply tax on top of my menu price
It will be calculated OK, you will see VAT [10%] = 10
Total cart = 110.00
B U T
2 - Menu prices already include tax
here ia a BUG in the calculation
Order Total = 100.00 is ok
VAT [10% included] = 10.00 HERE IS THE BUG
**it should be 9.09 !!**
because in this case the **net amount is 90.91 and VAT is 9.09**
