This happens 3-4 times a day, per cashier.

Cashier: Do you have a club card?
Customer: No, Thank you.
Cashier: Okay, your total is….
Customer: That can’t be right, it said [other amount] on the shelf!
Cashier: That’s probably the club price, would you like to open a free account?
Customer: NO, I already have a card.

I’m a cashier at my till pretty early in the morning (around 7:30). A teenage boy and girl enter, the girl is holding a flat iron that she brought in with her.
Boy: Hey, do y’all’s bathrooms have plug-ins in ’em? Like to plug stuff into? (*gestures to the girl and her flat-iron*)
Me: I’m fairly sure there aren’t.
Boy: That’s bullsh**t!
Me: You are welcome to check, but I’m almost positive there aren’t.
Boy: If there are, I’m gonna be mad at you!
Me (*sick of his attitude already*): Why?
Boy: ….. (*huffs off to the bathroom*)

No, there are no outlets in our bathrooms.

(I overhear this between a customer an employee at the return desk)

Customer: “I’d like to return this and get a refund. I didn’t like the flavour”

*The customer shoves a opened, half eaten chuppa chup to the employee”

Employee: “I am sorry ma’am, I cannot refund this. You have already opened it and half eaten it”

Customer: “WHAT?! You WILL give me a refund this. I DONOT like the flavour!. Give me my  refund of 35cents back!”

Employee: “I am sorry. But because you have already opened and half eaten this, I cannot refund it.”

*The customer stormed off*

(I work in the express lane, but if it’s super crowded I will sometimes hop on a register to help out. I’m not familiar with what all the produce looks like, and more than once I’ve asked the produce manager for help when picking an order. A woman comes through my lane with a lot of produce. I get through the produce I recognize first, and then pick up something I’ve never seen before.)

Customer: “Do you know what that is?”

Me: “No.” *I type in a number and charge her for it*

Customer: “Then how did you know what to charge me for it?”

Me: “There’s a sticker.”

(I show her where the sticker is with the PLU number on it.)

Customer: “Oh.”

I am a personal shopper at a grocery store and all our regulars know what we look like.

The person I am shopping for ordered eight or so bananas. All the bananas on the display are not great looking, so I get some better bananas out of the boxes below the display.

The first batch I picked didn’t have enough bananas. The second I turn to get more, an old lady comes out of nowhere and takes the first batch. She giggles at me and leaves before I can stop her.