SaleId (or whatever the PK is)
EmpId (or whatever the PK is for the file the sales people are on)
CommRate | if standard /default across sales.
CommRate | if overriding / or there is no standards
So for each sale you have as many records on tblSaleEmp as required for the
number of sales people involved in the sale.
There are many more variations depending on the complexity of your