Math function to round up the values to .0 or .5
<p>How can I round numbers up to the nearest whole <em>or</em> to the nearest half?</p>

<p>For Example:</p>

<pre><code>&gt; 23.15 --&gt; 23.5
&gt; 23.56 --&gt; 24.0
</code></pre>

<p>The rounding functions I know about are <code>floor</code> and <code>ceil</code>, but those only round to the nearest integer.</p>
