The jquery Rounded Corners module is a nice tool if you need rounded corners for divs, classes, blocks etc. I needed rounded corners for a container on my project, I'm using Blueprint 3 framework and this was really easy. The rounded corners module needs to be updated with the latest version, you can download it from here. Replace the version you have in you're Rounded corners module. First I had to create a class for my container:

Then I updated my page-front.tpl.php

And here is the code that goes in the Rounded corners configuration page within administer - site configuration: