title: objective-c round number to nearest 50
body: <p>How can I round a number to the nearest X value (for example 50)</p>
  
  <p>i.e 
  47 would be 50</p>
  
  <p>24 would be 0</p>
  
  <p>74 would be 50</p>
  
  <p>99 would be 100</p>
  
  <p>etc...</p>
  
  <p>I really have no idea where to start looking into how to do this...</p>
  
  <p><em>P.S. Im using cocoa-touch for the iPhone</em></p>
  
  <p>Thanks a lot
  Mark</p>