In other parts of the world there are specific customs when it comes to paying your local grocer or the hotel bill.
In France, most retail transactions are handled like this. Your bill comes to you on a tray. You pick it up and look at it and then you place your cash or credit card onto the tray and return said tray to the cashier. The cashier will then return your change or cash slip on the tray for you to take or sign.
In China and many other Asian countries, like Singapore, Hong Kong (OK, technically it's part of China but it's a Special Administrative Region), Taiwan and Japan, the cashier will present your bill with both hands and you should accept with both hands. When presenting cash or credit card for payment you present with both hands. It's a sign of respect from one party to the other.
Unfortunately, here at home, anything goes.