POS Software?

I have been selling my prints and decided after much encouragement to start doing craft/art fairs. I already use Bento 3 to keep an inventory of my prints but, what do you guys use for POS software? Maybe even something that interfaces with Bento 3?

I use a Mac and also have an iPhone if that would fit into any kind of solution you all might have.

Thanks for all the help.

-method

There are several POS apps for the iphone, just have to establish and account. You can get a wireless printer to print receipts, or better yet, email the receipts.

I was looking at Square Up from the makers of a service called Twitter you may have heard of. Link here: Square

What I'm interested in is something that will help me track my inventory so I can observe trends and sales history.