[http://www.checkoutapp.com/ 
]
[http://www.versionsapp.com/ 
]
Via [http://developer.apple.com/business/macmarket/checkout.html Apple Developer Connection]:
:The team of young developers at Amsterdam-based Madebysofa were frustrated as customers of a difficult point-of-sale (POS) application and a shortage of usable and affordable alternatives. So they decided to turn a problem into an opportunity, and set out to create their own application that worked the way they wanted. Their product is Checkout, is a powerful, friendly, and affordable POS system capable of running a small- to medium-size store, and is written exclusively for Mac OS X.
They also create a neat Mac OS X Subversion client.