How to generate Random numbers which are multiples of 30 in javascript

I Trying to generate random numbers that are are multiples of 30 in java-script that is

0 60 0 180 120 ...... and so on 
in range between 0 to 360 for example 

so i have function that

function (_range,_multi)
{
   Math.round(...);
   return rndNum;
}