uc_gst module

gistfile1.php

; @file uc_gst.info
name = UC GST
description = Add GST information to the checkout process.
core = 7.x
dependencies[] = uc_cart

<?php
/**
 * @file uc_gst.module
 * GST module for Ubercart
 */
 
/**
 * Implements hook_uc_checkout_pane().
 *
 * Add GST infomation to the checkout pane.
 */
function uc_gst_uc_checkout_pane() {
  $panes['gst'] = array(
    'callback' => 'uc_gst_checkout_pane_callback',
    'title' => t('GST'),
    'desc' => t("Display the GST applicable to the order."),
    'weight' => 1,
    'process' => FALSE,
    'collapsible' => FALSE,
  );
  return $panes;
}

/**
 * Callback for the gst checkout pane.
 */
function uc_gst_checkout_pane_callback($op, $order, $form = NULL, &$form_state = NULL) {
  switch ($op) {
    case 'review':
     $gst = 12.00; // You should do a calculation based on the contens of the $order object.
     $message = t('This order includes $@gst goods and services tax.', array('@gst' => $gst));
     
     $review[] = array('title' => t('Goods and services tax'), 'data' => check_plain($message));
     return $review;
  }
}