XpertMart lets you setup Employee Commission Groups and have different commission levels for different departments. You can periodically modify these commission levels to focus sales efforts on merchandise that needs a push.
22. Keep sales and store morale high with the right commissions for retail employees
XpertMart: Point of Sale and Inventory Control for Retailers
Before discounting your excess merchandise at the end of a season, try offering your salespeople bigger commissions on the items that must go. You would be surprised how effective your salespeople can be if you offer them a much larger commission than usual. This is an easy way to boost employee morale. It was money you were going to give away to the customer; why not give some to your salespeople instead?