Ian Parkhill's double gave the Bannsiders victory over Warrenpoint in the Section B clash at the Showgrounds.
The striker chested down from Neil McCafferty's cross before blasting in the opener after four minutes.
Parkhill fired home after the break but he missed out on a treble with a weak close-range shot into Parr's hands.
Warrenpoint, who face a relegation play-off, pulled one back with a rebound finish from Stephen Hughes after Jonny Frazer hit the woodwork.
It was a first home league win for Oran Kearney's side since December with Parkhill giving the hosts a perfect start.
Jamie McGonigle and Harkin also went close in the early stages for Coleraine while Warrenpoint rarely threatened in the first half.
Parkhill guided in from Harkin's good work to complete his double on 53 minutes but he squandered a glorious chance to add his third.
Frazer stormed forward and when his shot came off the post Hughes was in the right place to knock in the rebound with four minutes left.
Coleraine will finish the campaign in eighth while Town's top-flight status will be decided in a play-off.