Hi mranaconda2,
Edit component/com_digistore/digistore.html.php and delete this (line 565 aprox.):
<td class="sectiontableheader">
<?php echo _CART_DISCOUNT?>
</td>
<td class="sectiontableheader">
<?php echo _CART_TOTAL?>
</td>
Save the changes and check if all works fine.
Regards,
Note: maybe you need more changes...