I understand that a Bitcoin transaction, by design, will get one confirmation after an average of 10 minutes. Does that mean that a vendor that accepts Bitcoins will have to wait 10 minutes for a transaction to confirm? Let's say I am a sandwich shop and I decide to accept Bitcoins. A customer walks in and uses Bitcoin to pay for his sandwich. Do I, the sandwich shop owner, have to wait 10 minutes to confirm that he actually paid for the sandwich before I let him have the sandwich?