It would be great if it was possible to have a group of customers, for whom sales are summed for the purposes of eligibility for a given rebate percentage, while configuring the posting profile such that the rebates are paid/credited to each customer based on their portion of the total sales figure. From my testing, it seems that this is not possible. While sales are summed where a customer rebate management group is selected on the deal, on the selected posting profile, we must select fixed account and specify a single customer/vendor. This only works where the rebate amount is to be remitted/credited to a single customer.