Discount on order value

We want to offer this kind of discount structure by $ value; total order value $150 discount is 5%, then Total order value $300 discount is 10%, or on a quantity vlaue, i.e.; 2 or more items = 5% discount, 4 or more items = 10% discount. This is a enticement to order more or spend more. Thanks. New Zealand Zen site.:smile::cool:

You can do either of these things with the Quantity Discounts contribution.

http://www.thatsoftwareguy.com/zencart_quantity_discounts.html

Note that "Spend over $x" and "buy over <x> items" are mutually exclusive configurations; you can configure quantity discounts for one or the other but not both. See the help (above) for configuration details.

We have now installed the Quantity Discount module.
We have problems because; we are also running the Group discount module as well. The problem being, it causes double dipping from the invoice order subtotal. The tax calc is ok, but the final total does not balance correctly no matter what logical calculations I preform. I have tried tweeking all the true/false buttons, with tax, without tax, but have no satisfaction.

I would like the calculation to preform this way, either Sub Total then take off the 20% Group Discount, then take off the 5% Quantity discount,or vice versa, then the free shipping option, then the tax (12.5%), then the correct Total.

The invoice total I have been working on for the last 6 hours (am almost ready for a strong drink now!) is this:
invoice Sub Total $108.00 correct Should be: $108.00
Quantity Disc 5% -4.80 incorrect Quant D 5.40
Free ship option 0.00 correct 0.00
Group Disc 20% 18.53 incorrect Group D 20.52
GST Tax 12.5% 9.12 correct GST Tax 9.12
Total $ 81.79 incorrect Total shd be$82.08

How do I get the taxes to apply one after another, not from the same subtotal?
The tax total seems right but, the tricky bit is I cant get the total at the bottom correct ever!!!! It is so insane. Some one please give me an expert solution. Thanks guys. New Zealand website.:ohmy: