Workflow uc_vat uc_discount

Hello,

i have a problem with a french site that is online and working :((

an acountant told me that the vat is not applied where it should be.

they sell magazine with a vat rate of 5,5%
in this example we have 2 discounts applied using uc_discount_alt, free shipping and 5% off

if i buy 2 magazines at 20 each i should have

total : 40
total HT excluded : 37,92
5% discount : 36,02
vat : 1,98
total to pay : 38
++
shipping : 2
free shipping : - 2
shipping has no vat in France

this is what i get on the site (attached file)

total : 40
5 % discount : - 1,90
shipping : 2
free shiping : - 2
total HT excluded : 36,01
vat : 2,09
total to pay :38,10

I first noticed that the rounding is not done on each articles but on both (36,02 - 36,01)

and the VAT is not correct, customer pay 10 cents more, because it has to be effective once the discounts have been applied (on the vat excluded price)

Is there a way i could change the workflow to have a correct vat sum ?

do i have to change something in the uc_vat module or in the uc_discount_alt module ?

Thanks to all for all the work