The sales of the Tata Nano which crossed the ten thousand mark in the month of April have slowed down again in the month of May. The Nano has sold 6515 units only. However the Nano is the highest selling Tata car with the other models such as the Indica range (including the Vista) and the Indigo range (including the Manza) having been sold in the range of 5,400 range and 4,200 range. The Aria sold a dismal 37 units. Tata Motors sales have been falling and the company needs to tighten its act quickly.