Northamptonshire 171 (Robinson 4-55) and 172 for 4 (Curran 83*) beat Sussex 118 (Sanderson 4-32) and 222 (Finch 63, Wells 50, Cotton 5-48) by six wickets
Ben Curran's unbeaten 83 steered Northamptonshire to a six-wicket victory over Sussex at Wantage Road as the home side ended a poor season with a two-day victory.
Set 170 to win after Ben Cotton's maiden five-wicket haul helped bowl Sussex out for 222 in their second-innings, Northants slipped from 53 for 1 to 82 for 4 but Curran's solid half-century - his second in his five first-class matches since making his debut in August - and 51 not out from Adam Rossington saw their side home.
"It was tight, we've been in that position before," Northants coach David Ripley said. "The wicket was better than the first-innings scores suggested but you need somebody to get you over the line and step up Ben Curran.
"It was a really mature innings and we were in dicey territory still needing 80 to win four down and Ben played well and had Adam Rossington to help him finish the game off. We said the right things about trying to finish well and we actually delivered it so that's a pleasing thing."
Sussex collapsed from 114 for 2 after lunch and their season ended with a third successive away defeat - they have won only once away from home in 2018.
They had a chance to improve that record after moving into a good position just after lunch as Harry Finch and Luke Wells rescued Sussex from 5 for 2, trailing by 48, to raise a century stand for the third wicket as two batsmen finally got to grips with conditions after 20 wickets fell on day one.
But like day one, poor strokes outside off saw both Finch and Wells dismissed within three overs of each other - Finch for 63 caught behind off Ben Sanderson and Wells caught at first slip for 50 to become Cotton's first victim.
Ben Brown was then strangled down the leg side before a superb inswinger from Cotton saw Delray Rawlings record a pair in his only appearance this season. Michael Burgess chipped a catch to point and when Cotton ran a full, straight delivery into Danny Briggs' stumps, he completed his haul; 5 for 48 was a timely return playing for a contract next season.
There was a brief Sussex fightback as Chris Jordan and Ollie Robinson added 41 for the eighth wicket but Robinson edged a Nathan Buck lifter behind and Jordan ran himself out for 47 with only No. 11 Abidine Sakande for company.
It left Northants with a modest target but a challenge after a season of consistently failing in crucial moments of matches. Nerves were settled as Curran and Ricardo Vasconcelos - who clipped Jordan over square for a boundary to avoid a pair - added 53 for the opening wicket.
But Vasconcelos followed a Robinson delivery angled across him and edged to slip for 19 and it sparked a wobble as Charlie Thurston was caught at the wicket for 4 off a beauty from Robinson that went away from the right-hander, Alex Wakely edged to second slip and Luke Procter was pinned lbw for 1.
Procter's wicket was Robinson's 74th of the season - the most wickets in a season by a Sussex seamer since James Kirtley took 75 in the 2001 Division Two title triumph.
It was too much to ask, though, for Robinson to deliver victory as Rossington joined Curran to ease any tension and their sprightly unbroken stand of 90 brought a positive end to Northants' season of struggle.
"We didn't drive the game forward and we had the opportunity to after winning the toss on a good surface that just assisted the bowlers for the first 90 minutes of day one," Sussex coach Jason Gillespie said.
"To get bowled out for 118 you're not driving the game forward and even though we bowled them out cheaply they still had a lead and we saw the wicket had got better to bat on. Second innings we showed signs but we weren't able to drive home the advantage we created and it's been like that for the last month or so."