Meh. I worked retail for years. Sometimes, cashiers just want to strike up a conversation just to break up the monotony. I don't find it creepy at all. I appreciate that they are trying to at least pretend to be friendly, which, frankly, is their job.
I've seen much more creepiness from customers towards the cashiers. We had one guy who came in to buy, oh, some useless thing or another every week, just so he could flirt with the girl behind the counter. He would lean over, staring psychotically, and whisper, "You're such a pretty girl. I love your eyes. Let me take you out somewhere," etc. He was 60ish and she was 19. He kept on doing it until security had to show him the door. Scared the hell out of the poor girl. Then there were the tweakers who kept wanting to buy a gross of water purifier (ssshhyeah), and as you're standing there, explaining why you can't do that, they're scoping the joint out or going into withdrawal right in front of you.
And I won't even get into the pervs who bought ladies undergarments, just so they could take them to the youngest female cashier. The guy would moan and stroke the garments right there at the counter.