Change text in Commerce Kickstart "order total" dynamically
You can use the hook_commerce_price_formatted_components_alter()
The following example checks if VAT has been applied to the order total and changes the string accordingly:

/**
 * Implements hook_commerce_price_formatted_components_alter().
 *
 * Alters somes text at the checkout form
 *
 * @param $components
 * @param $price
 * @param $entity
 */
function mymodule_commerce_price_formatted_components_alter(&amp;$components, $price, $entity) {
  $pieces = explode('/',current_path());
  if(!isset($components['tax|ch_vat']) &amp;&amp; $pieces[0] == 'checkout'){
    $components['commerce_price_formatted_amount']['title'] = t('Order total (excluding VAT)');
  }
}