We love doing that too... Got 17 markdowns at £1 a pot the other day which has gone a long way to replace things that didn't survive the winter.
And yesterday, to contrast your till experience, we were taking sundry items to the DIY pay desk and a lad as cheery as anything stepped out with his code zapper, singing a song as he checked the items in the trolley - he got to a piece of wood dowelling that had no sticker on it and just shrugged - went to his till - rang up the total - was all smiles and cheeriness as we paid - and on to the next customer he went, as bouncy as he'd been with us - checking the receipt when we got to the car we saw that he hadn't charged us anything for the dowelling