The Hockeyroos started well and went ahead after five minutes when Georgina Morgan netted from a penalty corner.
Emily Smith extended the lead three minutes before the break before Grace Stewart made it 3-0 five minutes into the second half
Sophie Bray and Joie Leigh cut the lead in the final quarter but Danny Kerry's side were unable to level the score.
"We can take a lot of positives from the series," said GB captain Kate Richardson-Walsh. "That was probably our best performance today.
"We've not put in our best displays in the first five games so we can take from this that if we were able to stay level with Australia when not playing our best, hopefully when we are at our best we can beat them.
"The next six months are really busy. We have lots of games so we'll be match ready for the Olympics."
Australia beat Great Britain 3-2 in the final Test in Perth to take their six-game series 2-1.