I'm guessing by the time I get to the window to pay, they have already taken the person behind me's order, and know the expected price right? Sometimes I wish

I'm guessing by the time I get to the window to pay, they have already taken the person behind me's order, and know the expected price right? Sometimes I wish I had the option of tipping the fast food joint employees, as I think it would make them happier. Starbucks too, if you pay with credit card (as we are increasingly doing so), then we don't have that option anymore. To add to the last point, I'd like to be able to give money direct to the employees, as I feel they wouldn't get a fair piece of it if the company was allowed to disburse it.