Invoicing/inventory software

hi there, i'm looking for invoicing/inventory software for the mac. I am going to be running a small retail business and have to have all of my invoices and inventory all in one place.

Can anybody recommend some software for this? I would like to know what people like rather than just searching on google and getting whatever "looks good."

What does the apple store use to make their invoices anyway? is it just a non-consumer program?

Thanks in advance.