It is difficult and I woulkd probably have doen exactly the same!
Mind you it can pay off! Local Tesco which I rarely visit as my anti-supermarket rants here
are known! However my local "Offy" was closed so little choice. Took the Whisky to the checkout where the young man asked me £8.60, queried it and said that is what my till says, suggested he got a supervisor, who said she would be back -- returned with the Manager who said "put it through at £8.60" and this is for you Sir thanking you for your honesty and potentially saving xxxxx a lot of money. A voucher for £20!
So, I got my Scotch for less than half price and £20!
But, even if I had got nothing and paid the full amount, I would have felt good being Honest!
Meldrew