I'm trying to fix a problem with a site I inherited and looks like the math has been customized. What happens is this:

For products in which discount pricing has been configured using the Discount Price Manager the subtotal is erroneously reading the regular price for 1 unit but the lower true total is reflecting the discount correctly.

price each: .75
discount for 12 is .5833 - 12 should cost $7.00 although the closest it can get is $6.96

The subtotal is showing $9.00 and the total $6.96.

Can someone point me to the files I need to be checking where the calculations are done?

Thx