This integration was successfully tested on WP ecommerce plugin v 3.8.13.3

You can track per product information with this integration method.

1.

Edit template

In your wordpress installation, open and edit the file: wp-content/plugins/wp-e-commerce/wpsc-theme/functions/wpsc-transaction_results_functions.php

Find _function transaction_results._ Right below the line with function definition, there are global variables listed. Add another one there:

$wpdb

Then find the last line of the function:
_return $messagehtml;

2.

Integration

Put the following integration code ABOVE the line:

/*Post Affiliate Pro integration code */
$purchase = $wpdb->get_row( $wpdb->prepare( "SELECT * FROM `" . WPSC_TABLE_PURCHASE_LOGS . "` WHERE `sessionid`= %s LIMIT 1", $sessionid ) );

$message_html .= '
<script type="text/javascript">'.
"var sale = PostAffTracker.createSale();
sale.setTotalCost('".$purchase->totalprice."');
sale.setOrderID('".$purchase->id."');
PostAffTracker.register();
</script>";

/* /Post Affiliate Pro integration code */

In case you want to use tax and shipping variables, here you are:
_$total_tax
$totalshipping

3.

Per product integration

If you want to track commissions per product, just use this code instead:

/*Post Affiliate Pro integration code */
$purchase = $wpdb->get_row( $wpdb->prepare( "SELECT * FROM `" . WPSC_TABLE_PURCHASE_LOGS . "` WHERE `sessionid`= %s LIMIT 1", $sessionid ) );
$cart_items = $wpdb->get_results( $wpdb->prepare( "SELECT * FROM " . WPSC_TABLE_CART_CONTENTS . " WHERE purchaseid = %d", $purchase->id ), ARRAY_A );

$message_html .= '
<script type="text/javascript">'."";

$i = 1;
foreach ($cart_items as $item) {
  $item = array_map('wp_specialchars_decode', $item);

  $message_html .= "var sale$i = PostAffTracker.createSale();
    sale$i.setTotalCost('".($item['price']*$item['quantity'])."');
    sale$i.setOrderID('".$purchase->id."($i)');
    sale$i.setProductID('".$item['prodid']."');
    PostAffTracker.register();";
  $i  ;
}
$message_html .= "</script>";
/* /Post Affiliate Pro integration code */

If you want to use category name for the product ID, this is how to get it:

$category = wp_get_object_terms($item['prodid'],'wpsc_product_category',array( 'orderby' => 'count', 'order' => 'DESC', 'fields' => 'all_with_object_id'));

Then, the name is defined in:

$category[0]->name;

_
_

In case you want to use item name, use variable $item['name'] instead of $item['prodid'].

_
_

In case you want to use SKU, use this code first:

$item['sku'] = get_post_meta($item['prodid'], '_wpsc_sku', true);

Place it below the line with "arraymap" and then, simply replace $item['prodid'] with $item['sku']._

Do not forget to integrate your WordPress with the click tracking code. You can do it by placing the click tracking cade to your WP footer file, in Appearance> Edit menu of your WP.