The employee table does not count towards the reports and thus does not spoil the resulting margin. At the same time, it is not included in current open sales. It is thus possible to use price levels or discounts for employees on them without affecting the reports and statistics of your profits. The customer table, on the other hand, is included in the reports and whatever you mark on it will be stated in the reports.
You can read more about tables at this link: https://help.storyous.com/hc/en-us/articles/360000449765-TABLES