Javascript roundoff number to nearest 0.5

Can someone give me an idea how can i round off a number to the nearest 0.5.
I have to scale elements in a web page according to screen resolution and for that i can only assign font size in pts to 1, 1.5 or 2 and onwards etc.

If i round off it rounds either to 1 decimal place or none. How can i accomplish this job?

Write your own function that multiplies by 2, rounds, then divides by 2, e.g.

function roundHalf(num) {
    return Math.round(num*2)/2;
}

Here's a more generic solution that may be useful to you:

function round(value, step) {
    step || (step = 1.0);
    var inv = 1.0 / step;
    return Math.round(value * inv) / inv;
}

round(2.74, 0.1) = 2.7

round(2.74, 0.25) = 2.75

round(2.74, 0.5) = 2.5

round(2.74, 1.0) = 3.0

Just a stripped down version of all the above answers:

Math.round(valueToRound / 0.5) * 0.5;

Generic:

Math.round(valueToRound / step) * step;

To extend the top answer by newtron for rounding on more than only 0.5

function roundByNum(num, rounder) {
    var multiplier = 1/(rounder||0.5);
    return Math.round(num*multiplier)/multiplier;
}

console.log(roundByNum(74.67)); //expected output 74.5
console.log(roundByNum(74.67, 0.25)); //expected output 74.75
console.log(roundByNum(74.67, 4)); //expected output 76