[SOLVED] Rounded Corners

I'm trying to add rounded corners in the Montezuma theme to my text widgets in my sidebar. I have background colors for them now, so I'm not sure what the issue is.

I've tried adding rounded corners by adding to the .widget css and have had no luck.

I've added the below code in a bunch of different places hoping to get it to work but can't seem to figure it out

border-top-left-radius: 10px 5px;
border-bottom-right-radius: 10% 5%;
border-top-right-radius: 10px;

could anyone help me out? it would be greatly appreciated.