ifejza,
I was recommending creating a formula field (similar to Lockwelle) not changing the suppression formula.
To create a formula go to the Field Explorer, Right click on FOrmula Fields and seelct NEW.
Put in a name of the field. For this put in "New Grouping".
Hit OK.
Put your formula code in there and save and close it.
From here you can use this formula field like any other DB field.
Both lockwelle and I were recommending replacing your group level 2 with one of our formulas.
You would still want to have a group level 3 on the tax type and suppress the details.