Zakir,

We don't use it, really (it has some vestiges in currencies with "5 cent" and "25 cent" coins) - and not many other people do.

http://en.wikipedia.org/wiki/Quinary

Bases that have been used commonly by people include 2,8,16 (computer programming), 10 (many cultures in Europe and Asia), 10 divided as 2x5 (abacus, Roman numerals), 12 (dozen, gross, great gross; 19th century engineering and fine carpentry), 20 ("score" in Northern Europe, the Mayans), 60 (the Babylonians, "minutes-seconds" subdivision of time and angle.)

Math teachers use base 5 (and other bases) to "step outside" decimal notation when teaching about place value.

Good Hunting!
RD