Or even worse,they refuse to take 'the odd' because 'I've rung it in now'. I was always under the impression that it didn't matter what you rung in on a till,as long as you gave the right change for what you'd been given.
Depends on the shop but I work in retail and we teach in our checkout training to give change for what was rung in and not accept other money after the drawer is open in order to minimise the chance of being scammed.
It is a very well known scam for a customer to give one amount, then offer the odd change, then change their mind, then want specific coins in change and offer some money back to round up etc so by the end of the transaction the till is down and they've walked off with all the money and the items. Obviously most customers are not scammers but many retail workers don't want to take the risk.
Also I find that customers often aren't as quick getting the exact change from their purse/pocket as I am getting it from the till so, by the time they've fished the extra few coins out, I have already got the original change in my hand. If that is the case then it takes longer as I have to put every coin back into it's specific slot in the till (unlike dropping coins back into a pocket) before I can take the change from the customer, check it is correct, put it in the till and then get the correct change out of the till ... so it's easier all around not to accept the odd change on that occasion as it always happens when there's a massive queue and everyone is huffing about waiting
Personally if I have a customer who owes £16.01 and they have a £20 in their hand I will ask up front "You don't happen to have 1p or even the £1.01 do you? No problem if you dont, just trying to save you getting a handful of small change for the sake of the change in your pocket." Customers then either say yes or no and I can be inputting the total and getting the "rounded up" change while they're getting the odd change out and it expidites the entire process.
The cashier rung in that I gave them a £20 instead of £10 note. They then wanted me to sign the receipt to say the change was correct???
That's not a maths error though? They were covering their arse in case you used it to try and scam the store. If you went to customer services with a receipt saying you paid £20 and the change from £10 and claimed to be short changed then it would not look like a scam as the paperwork "checks out". However by having you sign the receipt they have proof that you have acknowledged that you did not give them £20 and so have not been short changed.