Because I always forget how to do it...

table-with-border-radius.scss

$table-rounded-border-color-outer: #ccc;
$table-rounded-border-color-inner: #ddd;
$table-rounded-border-radius: 5px;

.table-rounded {
  border-collapse: separate;
  border: 1px solid $table-rounded-border-color-outer;
  border-width: 1px 0 0 1px;
  border-radius: $table-rounded-border-radius;
  
  td,
  th {
    border: 1px solid $table-rounded-border-color-inner;
    border-width: 0 1px 1px 0;
  }
  
  thead th:first-child {
    border-radius: $table-rounded-border-radius 0 0 0;
  }

  thead th:last-child {
    border-right-color: $table-rounded-border-color-outer;
    border-radius: 0 $table-rounded-border-radius 0 0;
  }
  
  tbody {

    tr:last-child td {
      border-bottom-color: $table-rounded-border-color-outer;
    }

    tr td:last-child  {
      border-right-color: $table-rounded-border-color-outer;
    }
    
    tr:last-child td:first-child {
      border-radius: 0 0 0 $table-rounded-border-radius;
    }

    tr:last-child td:last-child {
      border-radius: 0 0 $table-rounded-border-radius 0;
      border-color: $table-rounded-border-color-outer;
    }
  }
}