Ask Slashdot: Business Software for Linux?
Delta asks: "I am currently looking into starting a company of my own and need a whole new area of software, to mange contacts, run billing systems, so I need software like SuperOffice and Point-of-Sale systems, but I want to run Unix! Can anyone recommend such software? And perhaps a good schedule prog? It's pretty obvious that I would need stability, I cannot have the system go belly up, as any bussiness would soon follow in such a case. Another advantage would be the ability to use the databases through a web interface, or being able to carry local copies on laptops and so on. All software under this topic is of huge intrest." Can Linux be used for those generic purposes in a sales-oriented business (read: Linux as cash-register?)
As for the POS software you're looking for, there are quite a few options available.
Samco has an extensive offering of business accounting applications that work with Linux, including POS. Check out the screenshots of their POS module. J.S. Software provides accounting and POS software, and they support Linux. LinuxPOS from Linux Canada is also available.
Funny how all three of these companies are Canadian. Don't worry about accounting tax differences too much, though--Canadian companies (have to) create software with other countries' tax laws in mind.