Could anyone tell me the best system for using Bitcoin or any other currency for a retail operation?
Bitpay or coinbase is probably your best bet. Good luck.
I am fairly certain that the OP is referring to a retail physical store, as in someone who is essentially accepting a 0/unconfirmed transaction all the time. I don't believe that coinbase/bitpay actually accept 0/unconfirmed transactions, although they do mark it as 'paid' once the tx is broadcast to their node.