manager being completely unfair, should i quit?

this is just a normal manager, at the sort of job where you earn minimum wage a lot of managers are crappy

if you're new you should be keeping your head down, not arguing if you get a telling off and if you need to ask a question (e.g. if someone asks for help with the bins should I help or carry on with my work) then watch the way you're asking it so you don't sound confrontational

if £10 is missing it's reasonable for people to get annoyed, if you take too long on your break (even if others do, they've been there longer and earned that), if you don't clean things which should be cleaned... and if you respond aggressively to criticism which it sounds like you have

you can quit if you like but you shouldn't assume another job will be any better

what because they expect you to do your job? it's hardly rocket science, as long as someone has told you how to work the till you shouldn't need much more