I am using Fixed Product Taxes (FPT) which we are calling a "Service Fee" to charge a $4 "Service Fee" for each item in the shopping cart. So if someone buys a quantity of 2, they are charged $8 extra.
This works great, but when I apply a "Promo Code" (Shopping Cart Price Rule) that should zero out the total for each item (including removal of the "Service fee"), it does not recalculate the Grand Total in the shopping cart, even though the discount appears and is calculated correctly. It seems like the recalculation is limited to the Product total, not the FPT amount.
I cannot post an image, but here is what the cart shows:
Product Line Item: $22 ($18 + $4 FPT (we call it a "service fee"))
Subtotal: $22
Discount (PROMO): -$22
Grand Total: $4
The total should have been calculated to be $0, since $22 - $22 = 0.
I have already tried setting "Apply Discounts To FPT" to YES in System > Configuration > Sales > Tax > Fixed Product Taxes > Apply Discounts To FPT
The Shopping Cart Price Rule uses a "Fixed Price Discount" of $22, when the product matches the SKU. Any amount over $18 (the product base price without FTP) has the same affect actually.
I am using Magento Community 1.6.1.0.