title: How to round decimal in Scala Spark
body: <p>I have a (large ~ 1million) Scala Spark DataFrame with the following data:</p>
  
  <pre><code>id,score
  1,0.956
  2,0.977
  3,0.855
  4,0.866
  ...
  </code></pre>
  
  <p>How do I discretise/round the scores to the nearest 0.05 decimal place?</p>
  
  <p>Expected result:</p>
  
  <pre><code>id,score
  1,0.95
  2,1.00
  3,0.85
  4,0.85
  ...
  </code></pre>
  
  <p>Would like to avoid using UDF to maximise performance.</p>