We just updated the Store shopping cart page to fix one long standing bug and to add a new feature.
The bug fix
For a while now the "Continue Shopping" link didn't populate properly if you choose to have it link to the last viewed category or the last viewed product. Well, that's fixed now. View the documentation for that link.
The new feature
There is now a way to empty the entire cart in on fell swoop. You can do it with a regular form post. Or you can do it with an AJAX post from the cart page or another page. View the documentation.