Send me a Private message and I may be able to help as I have used a few free ones in the past but there not that easy to get to grips with.
I set a basic one up for website stickers.http://www.shop.wikiwirral.co.uk/
I dont know tomato cart but the setup is pretty much the same. Its the qwerks when it comes to selling can be the problem.
Send a private message Click Me