Has an NBA game ever ended 89-76?
It has. 89-76 has been a NBA final 25 times in 73,172 games. The first was Minneapolis Lakers beat Denver Nuggets on December 10, 1949; the latest was Los Angeles Clippers beat Minnesota Timberwolves on March 9, 2015.
That makes 89-76 the 861st most common final score out of 3,189 that have ever occurred in NBA. One point away, 90-76 has happened 17 times and 89-77 has happened 33 times. Nearly all of its occurrences fall between 1980 and 2009. At one point the score disappeared for 29 years, between 1953 and 1982.