The latest deal at Brooklyn's Greene Avenue Market is an unusual one: 10% off if you pay with Bitcoin.

We were tipped off to this by Marc Hedlund, the VP of engineering at software firm Stripe, who Tweeted the following photo this morning from one of the market's locations:

— Marc Hedlund (@marcprecipice) November 10, 2013

We just got off the phone with Greene Avenue Market manager Dan Lee.

He actually had to call us back, as he was checking out a customer who just paid btc 0.013995 ($4.99) for milk.

He told us the sale has been on for a week as a promotion for what he believed was Brooklyn's first Bitcoin Meetup group. But the five Greene Avenue Market stores have been accepting Bitcoin since this spring, when prices began to climb.

We've been telling you why we think Bitcoin has some fundamental flaws.

But Lee makes a good case for why it's actually pretty great for retailers.

"There are lower fees, and you don't have to worry about chargebacks, which is beneficial for merchants," he says. "It's better than Visa or Master Card."

Indeed, Bitpay has zero transaction fees and only requires a monthly payment.

Bitpay also allows for instantly converting the Bitcoin into dollars, so Lee doesn't have to worry about the recent wild fluctuations.

All you need to pay for your groceries in Bitcoin is a phone with a Bitpay or similar app that can transact Bitcoin. Lee puts the dollar amount into his app, which shows the price in Bitcoin. A QR code for the transaction then pops up on his screen, and the customer scans it.

Lee says they now get 5 to 10 customers a week paying in Bitcoin, which may not seem like a lot, but it's up substantially from when they barely got any when they first started offering the service, he says.

But he plans to keep the sale on for awhile.

"We have no reason to stop soon, we don't do huge amounts of transactions, it's just so we can keep the interest alive."