Sydney will now take on Highveld Lions in the final to be played on Sunday.
The match went onto the wire and all three results were possible but Sydney ultimately reaped dividends due to a good opening stand.
The winners started the chase in right earnest as opener Steve O'Keefe hit off-spinner Eden Links for couple of boundaries. His partner Michael Lumb got two more in the second over from Ethy Mbhalati.
A flurry of boundaries from the duo saw Sydney reach 50 in the fifth over but Lumb was dismissed by Alfonso Thomas after scoring 33 off 19 balls. He offered a skier to rival captain Martin van Jaarsveld. Lumb hit six fours and a big six off Thomas.
O'Keefe however didn't let the momentum drop as Sydney maintained 10 per over run-rate. O'Keefe was finally bowled for 32 off 21 balls when he tried a wild slog of Links' delivery. He hit six fours.
However O'Keefe dismissal brought about a collapse as skipper Brad Haddin and glovesman Nic Maddinson who scored a quick 20 were back in the dug-out.
From 85 for one, Sydney team were reduced to 92 for four having lost three wickets in a space of 11 deliveries.
Moises Henriques then again steadied the ship with a brisk 27 that had couple of huge sixes but once he was gone, Sydney were 132 for seven.
But Cummins and Ben Rohrer ensured that the Australian team cross the finishing line.