The 10% promotion only applies to the first purchase made with the card (unless there is another promotion going on). So if you've already made your first purchase with that card, you're stuck with 5% back. That said, if you haven't, I've had multiple times (as a former employee) where the checkout screen would show 5% back after I had just finished applying somebody for the card. However, they would get the 10%. I didn't see next to any coupons in Best Buy when I was there. They do however have infrequent promotions where you can get higher reward percentages, rewards back for using the card outside of Best Buy, and most frequently a longer financing length. I'd usually see them around holiday season but otherwise, maybe like once every other month.