I have! They have a button on the register for "Post Coupon" and the cashier just hands me cash back. Be sure you show them your receipt, ask politely, and I guarantee you to get a yes!
Thanks.
It did work but I had to go to the original store I purchased from, which I still don't understand. The receipt was in the system and they would submit the coupon for their money, no matter what store it came from, I thought.
Repped you.