We (YoungPOS) just completed the Touch screen POS (Point of Sales) with Raspberry PI. We call it Raspberry POS and it could connect to Receipt Printer, Kitchen Printer, Barcode Scanner and Magnetic Stripe Reader (MSR). It is really full POS system for Restaurant and Retails. We could share this project to everybody who interested in POS solutions.
You could visit us at www.facebook.com/raspberrypipos to see these pictures/videos or you could share some information.
Full diagram POS system for restaurant (Touch Screen Monitor)
Simple diagram for retailer or restaurant without kitchen printer
Raspberry PI for Touchscreen POS
Full POS peripherals device (Printer, scanner, MSR)