It would be pretty rare for commissions in bike stores. That said my sister worked part time for a homewares store and yes, sales people were judged by the sales rung up under their code (check for this on the receipt).

The manager and full time staff member would often "jump in" on my sister's sales when she was on the till just to imput her code, esepcially if it was a large sale.

I'd say getting a bike in to try no obligation is a very good thing.