When sorting currency fields, I'm having issues with null, zero and negative values
<p>Given this HTML snippet, trying to sort currency values (where the values in parenthesis are negatives):</p>

<pre><code>&lt;td class="currency"&gt;$10.00&lt;/td&gt;
&lt;td class="currency"&gt;($5.00)&lt;/td&gt;
&lt;td class="currency"&gt;$5.00&lt;/td&gt;
&lt;td class="currency"&gt;($5.00)&lt;/td&gt; 
&lt;td class="currency"&gt;$5.00&lt;/td&gt;
</code></pre>

<p>In one case, ascending order displays as :</p>

<pre><code>($5.00)
$5.00
($5.00)
$5.00
$10.00
</code></pre>

<p>I believe that it should be:</p>

<pre><code>($5.00)
($5.00)
$5.00
$5.00
$10.00
</code></pre>

<p>How can this be sorted using jQuery to sort the intended direction?</p>

<p>In another case, the 1st six records have a null amount, the 7th has $0.00, the 8th through the 15th have null, and positive amounts start with $2.50 on the 16th record and beyond.  I believe that the null amounts should all be grouped together and displayed before the $0.00, $2.50, ...</p>
