i already voted. 
I have to say that this module is excelent. Congratulations.
The problem is that the discount that i make is on the final price with tax. For example i have a product that cost 18€. The final price will be 2.95€. So the discount is 15.05€ with tax. but the amout i had to put in the module is 12.54166667. This is the result that i need to have there so that with a 20% tax the final amount is 15.05€ with tax.
$this->add_prod_to_prod(171,1639,”$”, 12.5416666667);
$this->add_prod_to_prod(46,47,”$”, 14.2083333333);
$this->add_prod_to_prod(29,32,”$”, 16.7083333333);
$this->add_prod_to_prod(141,142,”$”, 11.7083333333);
$this->add_prod_to_prod(156,158,”$”, 18.3750000000);
$this->add_prod_to_prod(59,58,”$”, 8.3750000000);
$this->add_prod_to_prod(26,27,”$”, 16.7083333333);
$this->add_prod_to_prod(105,101,”$”, 12.5416666667);
$this->add_prod_to_prod(1643,1564,”$”, 9.2083333333);
$this->add_prod_to_prod(95,96,”$”, 16.7083333333);
$this->add_prod_to_prod(133,130,”$”, 6.7083333333);
$this->add_prod_to_prod(11,12,”$”, 5.8750000000);
for example. And because these are infinite number, multiplying then will not give the same result and the initial amount of reduction. In some cases there is an error of 1 or 2 cent. Its not the amount in question, but sound weird to the costumer to have a reduction of 15,06 or something like that.
It would be nice in the PHP to have an option to select with or without tax the reduction that is put on the module.
maybe you could address this issue later on 