Amazon is diving deeper into the payment processing business. The online retailer announced Amazon Local Register, a mobile point-of-sale service combining a mobile app with a secure card reader -- similar to Square -- that lets small businesses process digital transactions. The big draw for businesses would be Amazon's rate of 2.5% for every swiped transaction. Both Square and PayPal's point-of-sale services offer rates of 2.7%. Amazon is also launching a promotion that drops the rate to 1.75% if customers sign up before October 31. Money from transactions can be deposited directly into a bank account within one business day, or used on Amazon's website. "We understand that every penny and every minute counts," says Matt Swann, Amazon's vice president of local commerce, in a statement.