Sri Lanka had clinched the five-match series in the fourth game, but the loss narrowed the final score to 3-2.

Finch nominated Sri Lanka's ability to build bigger partnerships as the difference.

After bowling Sri Lanka out for 160 on Friday, Australia were reeling at 3-19 in the sixth over, after losing Finch (0) David Warner (10) and debutant Josh Inglis (5).

Wicketkeeper Alex Carey (45 not out off 65 balls) paced Australia's chase on a wicket offering extravagant turn, frustrating the bowlers with a series of sweeps as his team reached their target with 10.3 overs to spare.

Australia struggled early in their innings against the prodigious turn from offspinner Maheesh Theekshana (2-26 off 10), but the middle order showed more composure on a turning wicket than in the past, a pleasing sign before next year's World Cup in India.

Marnus Labuschagne (31 off 58) and Mitch Marsh (24 off 50) started the recovery, adding 31.

Carey and Labuschagne put on 51 for the fifth wicket, notching just one boundary in their partnership, skilfully manoeuvring the ball into gaps rather than playing risky shots.

Australia went 94 balls without a boundary and when Glenn Maxwell (16 off 17) was cleaned up by a superb delivery from impressive 19-year-old spinner Dunith Wellalage (3-42 off 10), they still needed 40.

But Carey and Cameron Green (25 not out off 26) steered Australia to victory with a breezy partnership, the latter ending the game with a six.

"We understand where our shortcomings come. That's no secret that we tend to struggle a little bit more in these conditions when they are turning big," Finch said

"The confidence in the group to get over the line in a tight run chase, albeit (only) 160, was still really important.

"Alex Carey played a really crucial knock there.

"Looking forward, we understand we've still got to continue to improve in these conditions but these were quite extreme compared to what we might face in India.

"I'm not sure I've seen the ball spin from ball one quite like it did today, so the fact that they (Carey and Green) weathered some really good bowling, particularly Theekshana, who was on fire, was really impressive."

Earlier, Sri Lanka produced their worst batting effort of the series, dismissed in just 43.1 overs after winning the toss.

They slumped to 7-62 and had lost eight wickets by the 25th over.

Chamika Karunaratne, who had a previous best ODI score of 44, displayed admirable resistance, scoring 75 off as many balls.

Frontline pacemen Josh Hazlewood (2-22 off 7) and Pat Cummins (2-22 off 6.1) and spinner Matthew Kuhnemann (2-26 off 10) bowled well and were assisted by some smart fielding and rash shots.

Finch revealed legspinner Mitchell Swepson had been down to play in the game but was forced out with a stomach bug.

Karunaratne was named player of the match and Sri Lanka batter Kusal Mendis (249 runs at 83) was player of the series

The host nation supporters showed their appreciation of Australia with many of those attending wearing a yellow shirt and others bringing banners thanking the visitors.

"It was outstanding, the Sri Lankan people are wonderful people," Finch said.

Australian Associated Press