Whats the best Point of Sale software that is used for one unit retail locations that also has inventory management.

I've been looking at premierpos and Keystroke POS.

I'm looking for one thats simple: all the cashier has to do is scan the items, select payment type and there done.

I would like to have options to offer multiple payment methods as well as some other basic features such as return/exchange, price change, discounts, item lookups, all the basic features.

I would also like it that when a particular item is scanned something pops up or is shown on the screen for the cashier to try to up-sell, cross-sell and accessory-sell.

I'm also thinking about adding a customer rewards program so I would need software that this will be able to keep track of and scan the cards right.