By Nick Mulvenney SYDNEY (Reuters) - Jordan Spieth has always said his first Australian Open triumph in 2014 taught him how to close out a tournament and the 23-year-old expects to reap an equally important dividend from Sunday's second victory. The 23-year-old American's win at The Australian Golf Club two years ago on the back of a final round 63 was the springboard to a stellar 2015 in which he won five tournaments, including his first two majors. At Royal Sydney on Sunday he prevailed after a gutsy three-under 69 and a three-way playoff with Australians Ashley Hall and Cameron Smith, which he won with a 12-foot birdie putt. More...