Rounding x.5 to the nearest even is designed to eliminate statistical anomalies. If you consistently round x.5 up, you end up over-estimating the average. For example, the average of 1.5, 2.5, 3.5, and 4.5 should be 3. But, if you round each value up you get 2, 3, 4, 5, which average to 3.5, which rounds to 4! But, if you round to the nearest even, you get 2, 2, 4, 4, which average to 3, the correct answer. Hence, the even rule. See http://en.wikipedia.org/wiki/Rounding#Round_half_to_even for more details.