Groupon offers the iRobot Mint 4200 Robotic Hard Floor Cleaner for $139.99 with free shipping. That's tied with our expired mention from three days ago and the lowest total price we could find by $20. It features wet and dry cleaning modes, smart guidance system to clean every square inch of floor, 3-hour cleaning on a single charge, and automatic shut-off. It cleans with micro-fiber cloths. Deal ends August 8.