The Pilgrims twice came from behind to earn a draw at The Jakemans Stadium, having trailed to Zack Kotwica's 11th minute header and Joe Hanks' 32nd minute drive.
Adam Chapman converted from the penalty spot on 29 minutes following a foul on Jack Broadhead and Robinson equalised five minutes from time.
United boss Adam Murray had made three changes ahead of kick-off, with Harry Vince, Louis Briscoe and Mani Dieseruvwe all returning to the starting XI.
City made all of the early running and Ross Durrant was forced to turn a Luke Hopper header on to the post.
The resulting Hanks corner was powered home at the back post by the head of KOTWICA to hand the Tigers the lead.
The Pilgrims had an equaliser chalked off when Dieseruvwe was adjudged to have turned home Jay Rollins’ fine cross with his hand.
United levelled when Reece King tugged back Broadhead in the box and CHAPMAN beat Jasbir Singh with a precise penalty to the keeper’s left.
Parity lasted only three minutes though, with HANKS rifling home a firm effort from the edge of the United box.
Tom Batchelor powered a gilt-edged chance wide following a long Chapman throw towards the half-time interval.
City went close after the break with Durrant saving at his near post to deny substitute Darren Mullings with his first touch.
A scrappy second half developed but United did level five minutes from time when Batchelor got in front of Singh to divert Chapman’s free-kick goalwards, with ROBINSON smashing the ball home from close-range.
The Pilgrims should subsequently have gone on to win, with Singh denying Rollins, Dieseruvwe having an effort deflected wide and the City keeper producing two further saves to deny Robinson headers in stoppage time.
Boston (4-2-3-1): Ross Durrant; Kalern Thomas (Liam Adams 79), Josh Robinson, Tom Batchelor, Jan Yeomans; Adam Chapman, Jack Broadhead; Jay Rollins, Harry Vince (Lewis Hilliard 58), Louis Briscoe (Karl Hawley 68); Mani Dieseruvwe. Subs (not used): Colby Bishop, Charlie Gatter.
Gloucester (4-1-2-1-2): Jasbir Singh; Keiran Thomas, Spencer Hamilton, Sam Avery, Bobby Moseley; Chris Knowles; Joe Hanks (Tom Webb 88), Reece King (Darren Mullings 59); Ed Williams; Luke Hopper (Joe Parker 90), Zack Kotwica. Subs (not used): Lewis Hall, Louis McGrory.
Referee: Kelvin Sarsfield.
Attendance: 1,094 (31 visitors).