
Originally Posted by
DrByte
The module that applies group discounts is:
/includes/modules/order_total/ot_group_pricing.php
But it works based on "product prices" supplied to it by the shopping cart. "Specials" and "Sales" are already applied at this point. All the pricing functions in the /includes/functions files are based around this same concept.
What you're asking for can be done, but is not a simple case of "just change this to that" for a few lines of code, and will require studying interaction of pricing functions, significant testing, and lots of patience.