The present invention is a robotic system for maintaining product inventory and dispensing products upon request from a customer or other user. Product items are stored in an inventory storage unit (ISU), one item per bin. Controller logic allows items to be stored in, and retrieved from, arbitrarily-assigned storage locations. The bins hang on rails within drawers. Upon a request from a consumer (or other user) for a plurality of product items, the robot retrieves a bin holding the first item from the ISU, and places the bin onto a shelf that moves with the robot. The additional items are handled similarly. Once all the items are on the shelf, the robot transfers them to a dispensing chute to the consumer.