title: Round down a numeric
body: <p>I have <code>numeric</code>'s like this one:</p>
  
  <pre><code>a &lt;- -1.542045
  </code></pre>
  
  <p>And I want to round them down (or round up the <code>abs</code>) to 2 digits after the decimal point. 
  <code>signif(a,3)</code> will round it down and give me 1.54 as a result but for this example the result I want is <code>-1.55</code>.</p>
  
  <p>Any idea?</p>