Bronson Xerri's contentious late try proved decisive as Cronulla Sharks boosted their NRL finals hopes with an 18-12 victory over St George-Illawarra Dragons.

Xerri charged over with five minutes remaining on Sunday after latching onto a high kick from Shaun Johnson.

The try was awarded, though Cronulla had to wait for confirmation it would stand as the video referee checked for a touch from Sharks' second-rower Wade Graham.

Cronulla's luck was in, however, with Johnson adding the extras to wrap up a win that moves the Sharks into the top eight, while the Dragons' have no realistic hope of making the finals.

Aaron Woods had got things started for the Sharks in the 17th minute, with Sosaia Feki swiftly doubling the home side's lead, but tries from Jackson Ford and Luciano Leilua either side of half-time had restored parity.

There was less drama at the SCG as second-place Sydney Roosters cruised to a 42-6 victory over New Zealand Warriors.

Roger Tuivasa-Sheck's second-minute effort put the Warriors ahead, but Latrell Mitchell and Joseph Manu put 2018 premiers Roosters in front by half-time.

Luke Keary's try had Sydney in complete control shortly after the interval and the hosts did not look back from there - James Tedesco, Brett Morris and Mitchell Aubusson all crossing over in the space of seven minutes.

Mitchell - who only kicked four of eight attempted conversions - helped himself to a second try soon after, before Daniel Tupou added further gloss late on.