Admin > Modules > Order Total
this is how mine is set up.
Code:
Order Total Modules
Modules Sort Order Action
COD Fee ot_cod_fee not installed
Discount Coupon ot_coupon 200
Group Discount ot_group_pricing 500
Gift Certs ot_gv not installed
Low Order Fee ot_loworderfee not installed
Shipping ot_shipping 400
Sub-Total ot_subtotal 100
Tax ot_tax 300
Tax Exempt ot_tax_exempt 310
Total ot_total 999
Important: check your settings for group discount.
This is how mine is configured:
Group Discount
This module is installed
true
Sort Order
500
Include Shipping
true
Include Tax
true
Re-calculate Tax
None
Tax Class
Taxable Goods
This setup works perfectly for me. I had the same problem as you, you might have found an old thread about it, and these settings were the solution, especially this "re-calculate tax" = none.
---Diana