A bank will not and can not transfer funds without your authorization. The only exception that I can think of would be a court order, but that's another issue.

A technique I "borrowed" from Steve Goodrich is to offer a 5% discount on the total amount due if the buyer pays with a US Postal Service Money Order. These are pretty hard to counterfit due to the watermark, and you know a USPS money order won't bounce. Worth the 5% to me especially if the sale is over $100. In your example 5% is $30. Well worth my time to make a trip to the PO for a money order if I were the buyer.