you can edit it directly in the PP-DirectPayment_PHP.php page like you have done, or you can edit the code for the item total in the checkout / confirm page to format it to 2 decimal places.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.