It's 2013, you can use CSS to achieve these rounded corners in all modern browsers, and degrade gracefully to non-rounded corners for older browsers. Something like the following:
/* rounded corners for the TH cells */
th:first-child {
-moz-border-radius: 6px 0 0 0;
-webkit-border-radius: 6px 0 0 0;
border-radius: 6px 0 0 0;
}
th:last-child {
-moz-border-radius: 0 6px 0 0;
-webkit-border-radius: 0 6px 0 0;
border-radius: 0 6px 0 0;
}
th:only-child {
-moz-border-radius: 6px 6px 0 0;
-webkit-border-radius: 6px 6px 0 0;
border-radius: 6px 6px 0 0;
}
/* rounded corners for the TD cells inside TFOOT */
tfoot td:first-child {
-moz-border-radius: 0 0 0 6px;
-webkit-border-radius: 0 0 0 6px;
border-radius: 0 0 0 6px;
}
tfoot td:last-child {
-moz-border-radius: 0 0 6px 0;
-webkit-border-radius: 0 0 6px 0;
border-radius: 0 0 6px 0;
}
tfoot td:only-child {
-moz-border-radius: 0 0 6px 6px;
-webkit-border-radius: 0 0 6px 6px;
border-radius: 0 0 6px 6px;
}
You can see an example with some colors here: Example on JSFiddle