It's been a very long time since I was looking for foolproof rounded corner solution for IE7 and IE8. curvycorners.src.js comes to rescue. What is does is pretty simple. It checks for '-moz-border-radius: 10px;' in the given CSS class and applies the same rounded corners in IE browsers.
Here is all in one CSS3 rounded corners and many other properties solution for IE7 and IE8. This is also nominated for 'Innovation of the year' in .net magazine awards 2011. CSS3 PIE (Progressive Internet Explorer):http://css3pie.com/documentation/getting-started/