This year's tally is already the Milanese club's biggest points total in a Serie A season since 2012-13, when they finished with 72 points, and they still have another four games to play.
"It was essential to win. In Rome (against Lazio) we did not do well and we knew that. Now there are four matches left and we must do more and more," Milan captain Alessio Romagnoli told DAZN.
The result extended Benevento's winless league run to six games and Filippo Inzaghi's side remain 18th on 31 points.
Milan were boosted by the return to fitness of top scorer Zlatan Ibrahimovic, who missed his side's last three league games through injury and suspension, and they looked far more dangerous with the talismanic Swede on the pitch.
Calhanoglu steered a shot into the bottom corner following a well-worked passing move after six minutes, and Hernandez threatened a second but was denied by a flying Lorenzo Montipo save.
Ibrahimovic came close either side of the break but on both occasions his finishes were blocked by the legs of the impressive Benevento goalkeeper, before Iago Falque drilled a fierce shot just wide for the visitors.
Montipo appeared determined to frustrate Ibrahimovic as he charged down another effort from the 39-year-old.
But Milan eventually doubled their lead when Montipo could only parry an Ibrahimovic shot into the path of Hernandez, who fired home the rebound.
Gianluca Lapadula's glancing header was narrowly wide for the visitors, but Milan held on for an important win ahead of their visit to Juventus next Sunday.