h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Ah yes but what you have failed to mention is the 2 dreaded sentences.
Have you got you super123club card? and would you like some cashback?

Im a cashier and there are a couple of annoying cashback scenarios that happen all the time:
1. Cashier: "Would you like cashback?"
Customer (confidently): "No"
(Cashier presses "no" button on till, till thinks for a while, then starts to print our slip)
Customer: "Oh wait, yeah, I'll have £30."
Cashier smiles though gritted teeth and has to cancel the transaction, carefully rip up the slip, swipe the card again, type in the cashback and wait for the till to have a good think again.

2. You have just done a "flight" (i.e. bagged up just about all of the money in the till and sent it up to the cash office) and there is only about £40 in notes in the till. The next three customers all ask for large amounts of cashback. You try and bargain with the third one who is invariably posh, saying "well, I dont have much cash in the till, I could do £20 for you... " (which would be made up of a couple of five pound notes and the rest in coins, which you have almost run out of as well) and the get abuse hurled at you "Thats not good enough! I want £50!!! What kind of shop is this!"

I worked as a till monkey myself not too long ago, and fortunately people did tend to stay the course as to whether they wanted cashback.

However, during Christmas season, a weird condition overcomes all shoppers in Ireland which prevents them from using any currency other than €50 notes. This results in some rather annoying exchanges.

Monkey: That comes to €101.23 altogether, please.
Customer: Here you are *Hands over €150 in €50 notes.*
Monkey (dying inside): Thank you (keeping up an impossible facade of chirpiness). *Deposits cash, hands over receipt and change in €5 notes and some precious coins. Till is now almost empty.*
Customer: Thank you. Oh, I have a clubcard...
Monkey: I'm sorry sir, I can't take this after the transaction is finished...
Customer: [CENSORED]
*During rant, monkey manager, who manages to placate the cutomer. Customer eventually walks off with food worth half the monkey's weekly wage.*
Customer2 (visibly p1553d off as she had to wait 20 minutes to buy a pack of chewing gum) Just this please. *Hands over gum.
Monkey: That's 29c, please.
Customer2: *Hands over €50 note.*
Monkey: You don't have anything smaller?
Customer2: No.
Monkey: Ah, well, it's just that I can't give you change...