I have to agree with Pickle on this one. Years ago I would have pointed out the mistake - I'm 54 btw - but now I think it's a case of "swings and roundabouts". Last week, for example, the girl in the Co-op never gave me my change. Unfortunately I didn't notice until I'd left the shop. I could've went back and kicked up a fuss but seeing as it was only about �1.40 I didn't bother. Besides, the girl was new and I didn't want to get her in trouble.
This morning I went to the Aldi and was only charged �3.54 instead of �5.54. Again I didn't notice until I got home. To be honest I did think about going back but nah, why bother? .. Like I say, swings and roundabouts :)