The two homers -- Rodriguez's to right field, Posada's to left -- erased a 1-0 Twins lead.
New York added two more runs in the ninth on RBI singles by Robinson Cano and Posada.
The Yankees advance to the American League Championship Series against the Los Angeles Angels, who also swept their division series, defeating the Boston Red Sox 7-6. Game 1 is scheduled for Friday in Anaheim.
Joe Mauer singled in Minnesota's run in the sixth inning.
Andy Pettitte was the winning pitcher. Carl Pavano took the loss. Each team collected seven hits.
The game was the last in the Metrodome. The Twins will play in a new facility, Target Field, starting next season.
Copyright 2009 by United Press International.