I would normally mention something about it, just to make sure. Here is a related story: I went to the Home Depot with my family, as my dad was laying down some serious cash to buy big time woodworking tools to build some cabinets for his shop. To make a long story short, we got out to the vehicle with the merchandise, and my dad looked at the reciept, thinking something sounded funny. It turned out that they didn't charge him for an $800 item! So, he went back in, and let them know, and got it all taken care of. He was kind of kicking himself, but he knew he had to do the right thing.