This was actually the (first) reason we added the tax classes: to show
them in columns on the invoice—without the class we would need a column
for each tax rate, even though they are the same tax.
The invoice design has the product total with taxes at the last column,
above the tax base, that i am not so sure about, but it seems that it
has not brought any problem whatsoever so far, so it remains as is.
Had to reduce the invoice’s font size to give more space to the table
or the columns would be right next to each other. Oriol also told me
to add more vertical spacing to the table’s footer.
