England and United captain Rooney headed into Sunday's match amid an unusual media furore after footage emerged of him being supposedly floored in a mock boxing bout with Stoke City full-back Phil Bardsley at his home.
Rooney ensured he had the last laugh with a boxing-themed celebration when he put United 3-0 ahead in the 34th minute, completing a first half where nothing went right for the visitors at Old Trafford.
Having won six and lost two of their previous nine Premier League matches in 2015, Mauricio Pochettino's Tottenham team headed north with hopes of drawing level on points with their fourth-placed opponents.
But they were faced with a relentless United side as goals from Marouane Fellaini and Michael Carrick inside the first 20 minutes set Louis van Gaal's men on the way to a victory that leaves them just two points behind misfiring neighbours Manchester City, who are second.
The excellent Carrick was one of three players to come into the United line-up following Monday night's dispiriting FA Cup quarter-final loss to Arsenal, alongside Juan Mata and Phil Jones, while Danny Rose was preferred to Ben Davies at left-back in Tottenham's only change.
But more sizeable holes in Tottenham's defensive set-up were soon apparent as Carrick strode into midfield unchallenged to play a measured throughball that Fellaini steered across Hugo Lloris and into the bottom corner in the ninth minute.
Roles were reversed 10 minutes later when Fellaini's attempt from Mata's in-swinging corner was partially cleared and Carrick calmly picked his spot with a fine header against his former club.
Dembele wasted a rare opening for Pochettino's men early in the second half, while Bentaleb made an important block to thwart Daley Blind at the other end.
The earlier ferocious pace had understandably subsided by the time that Ander Herrera lashed into the side netting in search of United's fourth.
Tottenham suffered no further damage, but their first defeat in six outings against United had long since been a formality - in-form striker Harry Kane prevented by De Gea from reducing the arrears in the 89th minute.
