I do a quick scan as have been hit a few times. Once was a bizarre scan for bottle of expensive booze that was no where to be seen or near the till, but it added £20 to the bill and I’d blindly just paid then realised on the receipt before walking out the shop.
Also I insist on the receipt when asked “would you like your receipt?”. Yes I would as I’ve just seen it’s been printed anyway, so if I say no you chuck it away. I may as well have it. Plus in co-op if you ask for the receipt you get the money off coupon for next shop, but don’t otherwise.
So having made the effort to ask for the receipt, I give it a quick check.
Would be great if receipts could be online though. Tie it up with reward cards maybe, log in and there’s the receipt.