According to sportsdatabase.com, there were 772 games settled by 1 point in the NBA during calendar years 2009 and 2010. There were a total of 18,616 played during that time.
That would leave 772 / 18,616 = 4.15%
There were 1,119 games settled by 2 points during that time.
1,119 / 18,616 = 6.01%