In version 6.4.3 it worked correctly but in the latest versions (8.X.X) it does not calculate correctly the VAT of the grouped product when it has a discount. The calculation it does is to apply the VAT to each of the products without the discount. For example, a grouped product that has 2 products each worth 60 euros, the total is 120 euros, but a discount of 20 euros is applied, which makes a total of 100 euros. The VAT should be 21 euros but your plugin gives as a result 25,2 euros (taking into account the VAT of the two products). As I said in the previous versions it worked. In the configuration I have not selected the fixed prices, they are calculated automatically.
In version 6.4.3 it worked correctly but in the latest versions (8.X.X) it does not calculate correctly the VAT of the grouped product when it has a discount. The calculation it does is to apply the VAT to each of the products without the discount. For example, a grouped product that has 2 products each worth 60 euros, the total is 120 euros, but a discount of 20 euros is applied, which makes a total of 100 euros. The VAT should be 21 euros but your plugin gives as a result 25,2 euros (taking into account the VAT of the two products). As I said in the previous versions it worked. In the configuration I have not selected the fixed prices, they are calculated automatically.