One of our shops does that, she takes 15% off the total price regardless of the yardage. She also has stash cards that are stamped for each $5 purchase. It takes $100 to fill the card, worth $10 off next purchase. None of the LQS allow the card to be stamped for sale or reduced items but that it okay with me. The other LQS keeps track of your spending, when you reach $300, you get a $20 gift card.
Again, no sale items are allowed to be a part of that total.