oddities at the cashier

I went to PetSmart this afternoon to buy a covered little box for my cat. He's got this horrible habit of throwing litter out of the box when covering his "business" and it's really messy and annoying. Anyway, when I went up to pay, there was but one person in front of me. Her bill -> $17.44. She wanted to pay with a Visa gift card. These things are just like normal gift cards but work anywhere Visa is accepted - it's like a prepaid credit card. So she goes to use it and it comes back declined. Then she tries again with the same result. The cashier, trying to be helpful, asks how much is on it and she replies that it only has a couple dollars left. Gee, I wonder why it didn't work? They call the manager out who has the idea that we'll just charge $3.00 to it and then she can pay the rest. OK, we're down to $14.44 due. She hands the cashier fifteen dollars in cash. And says that she wants to pay $13.00 and then charge the remaining $1.44. So she does. She runs her Discover card for $1.44 and gets two one-dollar bills back. So for this $17.44 purchase, she paid $3.00 on a gift card, $1.44 on a Discover card, and then $15.00 in cash and got back $2.00 in cash. This whole ordeal took about fifteen minutes. I just don't understand. :)