The Premier League side scored each of their five spot-kicks to seal an International Champions Cup victory against the Serie A outfit, setting up Saturday's clash with Real Madrid
The Red Devils scored each of their penalties, with captain Darren Fletcher converting the decisive kick after Marco Andreolli rattled his effort off the crossbar.
The result preserved United's perfect record in the United States, with three wins from three, including two in the ICC, which means victory over Real Madrid on Saturday will earn the English outfit a place in the final.
Red Devils manager Louis van Gaal made four changes to the starting XI that took to the field in the 3-2 victory over Roma on Saturday, with Anders Lindegaard, Chris Smalling, Fletcher and Ashley Young returning to the line-up for their reunion with former United captain Nemanja Vidic.
Inter made just one change to the team that beat Real Madrid on penalties in California on Saturday, with Joel Obi dropping out for Rene Krhin.
A number of United youngsters were given game time in Denver but the return of senior personnel was clearly a boost and it showed early on, with the Premier League side coming close to breaking the deadlock in the 10th minute.
United defender Phil Jones stooped low to direct his header towards the bottom corner of the net but Inter goalkeeper Samir Handanovic got his hand to the ball and denied Jonny Evans on the rebound in a goal-mouth scramble.
There were few clear-cut chances throughout the first half, though Wayne Rooney, Juan Mata and Danny Welbeck cut the Italians apart with a thrilling passing move, only for Mata's low cross to be cut out before it reached Rooney.
Wilfried Zaha was the only player in United's travelling squad not to have played a minute prior to Tuesday's clash but he was given time in the second half and came close to netting the opener within minutes of his introduction after a driving run from halfway.
Van Gaal had said Zaha is incapable of filling one of his wide roles next season and the former Crystal Palace man was deployed up front on Tuesday.
Luke Shaw, the €36m arrival from Southampton, came on at the break 24 hours after his new boss had declared him currently unfit to carry out a left wing-back role.
Nani went close for the Premier League side, cutting in from the right and exchanging passes with fellow substitute Shinji Kagawa, but his right-footed strike went over the bar. Shortly afterwards he forced Juan Pablo Carrizo into a routine save with a low shot after he was picked out by Fletcher.
In between those two efforts Tom Cleverley almost broke the deadlock himself, but his volley from just inside the area flew over the crossbar.
Van Gaal's men then thought they should have had a penalty when Cleverley was brought down in the area, but the referee was unmoved despite what appeared to be a clear trip.
Inter almost won it at the death after being awarded a free kick, but David de Gea denied Fredy Guarin from 25 yards out.
With neither side able to find the breakthrough the match went to penalties, and with Ashley Young, Javier Hernandez, Cleverley, Shinji Kagawa and Fletcher all on target the Red Devils picked up two points for the penalty victory, leaving them top of the group with five.
Inter lie in second having taken two points for their penalty win against Madrid, plus one for the defeat here.
United face Madrid at Michigan Stadium on Saturday, while Inter face Serie A rivals Roma on the same day.