Round numbers

I need to round a result number,by precision;

Example:
Math : y=x/1000000; x=5 => y=0.000005,
but if I do this in java script y=0.00000500001;(not right) ;how do I round a equation by precision to have a math result

 

On this page: http://www.merlyn.demon.co.uk/js-rndg3.htm you'll find several methods (arithmetics, strings manipulations, ...)

 

<script language="javascript">
function php_like_round( num, pre )
{
 	var temp = '1';

 	for( i = 0 ; i < pre; i++ )
 	{
		temp += '0';	
	}
	return Math.round( num * temp )/ temp ;
}
document.write( php_like_round( '4039.23344534534', '2' ) );
</script>

HTML:

that works .....

 

thx very much