Vielleicht 'to turn a blind eye to' oder 'turn a deaf ear to'. Würde vom Sinn her passen.

What does the literal translation mean please? I' m obviously missing some cultural reference here - please would someone explain about letting 5s be.
Thanks.

da gibt es doch auch so eine Redewendung mit "slack", wenn sie mir nur einfallen würde...

In other words giving in a bit to someone (the customer) for the sake of peace even if someone is wong.
Giving slack comes from letting a rope or line loose a bit like in fishing
"Fünfe gerade" means let five be an even number. Get it?

I think it's to do with maths, as in normally you'd say 5 is an uneven number (ungerade), but sometimes you just have to let things be not quite right without making a fuss or doing anything about rectifying them.

I actually know it mainly from letting a mess be a mess, sitting back and relaxing in a flat full of household chores going begging, etc.