PC12 PLT EXPERIENCES NMAC WITH ANOTHER ACFT AT AN UNCONTROLLED ARPT. LATER DISCOVERS INCORRECT CTAF FREQUENCY TUNED.

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I WAS ROLLING OUT ON A 2 MI FINAL APCH TO RWY 16 AT BMC; WHEN THE TAS ALERTED; JUST AS I SAW A TWIN ENG ACFT APCHING NEARLY HEAD ON. I WAS NOT SURE IF IT HAD TAKEN OFF ON RWY 34 AT BMC; OR HAD JUST OVER-FLOWN IT. THE ACFT PASSED OFF MY L WING; CLBING. I HAD ANNOUNCED MY POS SEVERAL TIMES INBOUND TO THE ARPT; AFTER CANCELING MY IFR CLRNC ABOUT 20 MI OUT; BUT HEARD NO OTHER RADIO TFC ON CTAF FOR BMC; OTHER THAN A HELI; BUT I COULD NOT DETERMINE WHICH ARPT IT WAS AT. DURING ROLLOUT; I HEARD A RADIO CALL TO A 'MALIBU' LNDG AT BMC ON RWY 16; APPARENTLY FROM THE TWIN I HAD SEEN; ASKING IF IT WAS ON THE RIGHT FREQ AND IF IT HAD SEEN THE TWIN. I THOUGHT IT MIGHT HAVE BEEN FOR THE PILATUS I WAS FLYING. I RECHKED MY RADIO FREQ AND FOUND THAT I HAD DIALED IN 123.00 FOR CTAF; INSTEAD OF THE PUBLISHED 123.05. CONSEQUENTLY; NO ONE AT BMC HAD HEARD MY RADIO CALLS; NOR HAD I HEARD THEIRS. BIG ERROR ON MY PART; WHICH COULD HAVE RESULTED IN DISASTER. THE TAS WARNING WAS A GOOD HEADS UP. NEITHER ACFT TOOK EVASIVE ACTION. I WILL CERTAINLY TAKE PAINS TO DOUBLE/TRIPLE CHK RADIO FREQS IN THE FUTURE.