Only those accessory uses and accessory buildings customarily appurtenant to a principal use, such as incidental storage facility, garage, or off-street parking area. Accessory uses such as gift shops, newsstands, pharmacies, deli or coffee shops (outdoor seating permitted if located within fifteen (15) feet of building), beauty/barber shops and tanning salons, and employer operated day care facilities shall not exceed a cumulative floor area of twenty (20%) percent of the floor area occupied by the primary use.