Om Sai Ram!
Here is the significance of Tarak Mantra. I got it while reading a book on our beloved Baba.
"Om Sai, Shri Sai, Jai Jai Sai"
This Mantra has been coined on the basis of the Mahamantra of Lord Ram - 'Shri Ram, Jai Ram, Jai Jai Ram' which is a Siddha Mantra adopted by many sages and saints in -the ages past. It seems Revered' Shri Sivanesan Swamy of Shirdi is the person who has made this Mantra popular and contributed immensely to its chanting far and wide. Today this Mantra is chanted by Sai devotees not only in India but all over the world. In this Mantra, Baba's name is repeated thrice.
Some twenty years back, nobody knew of this Mantra as the Tarak Mantra of Baba but some devotees had already coined it and they were chanting it along with other mantras in their pujas.
Baba had said that if one merely chanted 'Sai, Sai', from the core of his heart, He shall come running even from across the Seven Seas. From this it follows, that in a Mantra what is more important is the name of Baba and the devotion with which it is chanted, and not the Prefixes and suffixes added to it, which seem to be aimed at making the Mantra melodious. As a particular Mantra is chanted by more and more people with devotion, it acquires more and more potentiality.
I might venture to suggest that the choice of a Mantra (if given by a self-realised Guru) should be left to the devotee himself who may acquire one in a natural and according to his own temperament. It is experience that the chanting of mere Sai, Sai or ever 'Baba, Baba' putting heart and soul in the words, is much more blissful which no amount of melodious singing with accompanying musical instruments, is capable of providing. The 'Bhav' in chanting is more important than the words.
(Source: Scribblings of A Shirdi Sai Devotee
by Suresh Chandra Gupta)
Let our faith be strong & patience be unshaken!
Om Sai Ram!