If you mean this feature on Invoice processing:
Apply a discount or surcharge to Actual price
then no, all that does is apply real-time changes to the Actual price column. The change itself is not recorded anywhere. If you don't save after applying it, then the change is lost, since all it does is alter those values in the Actual price column.
Member fees is an entirely different feature. Those are calculated from each user's member fee set on
User maintenance.