how to round up to the next x20 number with php?
<p>I know ceil, which will round 15.1 to 16 and 31.2 to 32.
But how to round up to the next x20 number? like 15.1 to 20 and 31,2 to 40?</p>

<p>Is needed to make sensefull labels for the y-axis of a chart.</p>
