I'm trying to setup a tax rule for the Australian GST on my shopping cart, which is rather simple, it is a straight 10% tax on everything.. The problem i'm having is all the products are listed with a tax inclusive price, so I need to work in the following calculations somehow:
Cart sub-total = ((total price of cart) * (1/1.1))
Tax = ((sub-total) * 0.1)
Grand Total = ((sub-total) + (tax))
Where can i enter these calculations in the ecart? or in the code?