In that case I recommend that you go to your bank and make a cash withdrawal in the form of $2 bills. That way you can be cool when handing out cash tips.
I do all my banking online. My bank doesn't have any local branches. Seriously, who has cash anymore?
There is a worldwide network of machines that do nothing but give cash out from your bank account. Judging by the number of them I'd wager that almost everyone has cash.