Pinnacle Cart

For web development projects that require a shopping cart, I recommend and utilize Pinnacle Cart.  

I have found many clients prefer to synch their shopping cart with an installed version of Quickbooks such as Quickbooks Pro instead of the online version. It's tough to find a cart solution that will synch with these installed versions without an upsell or 3rd party solution.

Pinnacle offers a Quickbooks auto-synch function with their Small Biz plan and higher.

Check them out.