Thank you, Jason.
It appears that the discounts are working. I have one other question...
Since the discounts are leaving a balance due of $0.00, PayPal Standard (which is my primary merchant account) will not accept the transaction. PayPal returns an error.
Is there a way to process the transaction while redirecting the user to a webpage other than PayPal when there is nothing to pay for?
Thanks again for all your help!