You will need to use the CSS border-radius attribute. But it's a bit more complicated than simply adding that code to the table CSS. See http://stackoverflow.com/questions/628301/css3s-border-radius-property-and-border-collapse collapse-dont-mix-how-can-i for more inforation.
Personally, I'd be tempted to just use a background image to produce the rounded corners. Then overlay that with the cell data.
Just thinking out loud... Rick
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