In addition to Mr Lakshmipathi's suggestion--You can settle the customers in either ways in SAP as mentioned below:
1.Without material movement:Reducing the Account receivables by raising some credit memo or rebates procedure....
2.With Material Movement: You can raise the free goods delivery process for this 5$.(SO type SDF-Subsequent free of charge delivery or ZERO Billing with free samples process)
Note: What to follow will be at client's discretion.
Phanikumar