That Software Guy! eCommerce Starts Here!
If you are using any of my discounting software, running the popular Zen Cart mod Sales Report against an order with one of these discounts will cause the totals not to add up correctly.

The fix is to modify admin/includes/classes/sales_report.php as follows: search for

          elseif ($class == "ot_coupon" || $class == "ot_group_pricing" || $class == "ot_better_together") {

and add in the classes you are using.

A complete list of the classes I have created for discounting is:

Better Together: ot_better_together
Big Chooser: ot_big_chooser
Big Spender: ot_bigspender_discount
BOGO: ot_bogo_discount
Case Discounts: ot_case_discounts
Combination Discounts: ot_combination_discounts
Free Gift Chooser: ot_freegift_chooser
Free Gift Spender: ot_freegift_spender
Frequency Discounts: ot_frequency_discount
Quantity Discounts: ot_quantity_discount
Table Discounts: ot_table_discounts
Newsletter Discounts: ot_newsletter_discount
Manufacturer Discount: ot_manufacturer_discount
Military Discount: ot_military_discount

This list was originally posted on my blog, but putting it here allows me to keep it up to date more easily.