Add CSS classes to order total preview line items

I tried this code with a custom module to remove subtotal from order total preview pane in checkout page but it doesn't work. How can I remove "subtotal" and just show "total" ?

 
function uc_hide_subtotal_line_item_data_alter( &$items ) {
  foreach ( $items as &$item ) {
 if ($item['id'] == 'subtotal') {
     $item['callback'] = NULL;  
     }
  }
}