Its been a long time since I worked retail, but I remember the costs of cash handling to be quite a bit more than you might assume:

-Count cash drawers in and out for every employee, every shift

-Count cash payments received & change returned

-Prepare daily bank deposits

-Take daily bank deposits to bank, get more change

I couldnt say exactly what percentage all of that adds up to, but I could see it being 3% or maybe even more.