Mahindra and Mahindra (M&M) has posted a 15.7% increase in its tractor sales for June 2005 at 7,879 units as compared to 6,812 units in the same month last fiscal.Tractor sales for the first quarter ended June 2005-06 increased 32.1% to 21,200 units as compared to 16,048 units in the same quarter of the previous fiscal, M&M said in a release today.