You could, for example, add the following macro to your mailmerge main document, then save it in the .docm format before running the mailmerge.
Code:
Sub MailMergeToDoc()
Application.ScreenUpdating = False
Dim t as long, r As Long
ActiveDocument.MailMerge.Execute
With ActiveDocument
For t = .Tables.Count to 2 Step - 2
With .Tables(t)
For r = 5 To 2 Step -1
Select Case r
Case 5, 4, 2
If Split(.Cell(r, 2).Range.Text, vbCr)(0) = "$0.00" Then
.Rows(r).Delete
Next
End If
End Select
Next
End With
Next
End With
Application.ScreenUpdating = False
End Sub
For PC macro installation & usage instructions, see:
Installing Macros
For Mac macro installation & usage instructions, see:
https://wordmvp.com/Mac/InstallMacro.html