Who is the change for?

I work as a cashier in a small fry shop. (Don’t think mcdonalds, think takeway with a few tables lol.)

And when someone says “keep the change” I’m always confused, do I just not give the change back, or is the change meant for me, as sort of a tip? I’ve never taken the change for myself, and to be honest it would probably take more effort and time than it’s worth for a few cents. Keep in mind, I live in Europe where giving tips is basically unheard of. I dunno I was just wondering lol

Cheers!