We had the same issue and settled on Microsoft Excel. Heritage Auction has a free one online that we also started an inventory there, but gave up and went back to Excel. We had difficulty getting HA program to accept the numbers from our NGC slabbed coins, they did fine with PCGS, but not NGC.
I got frustrated with it and gave up.
Another member here helped us with the Excel program and it even has the ability to link back to iphoto and our images. You can customize it to whatever info you want to have and it was already on both of our MacBook's, so it didn't cost anything extra. If you do a search on this site for "coin inventory software" I think you'll be able to find a good bit of info to help you. Good Luck!
