title: How to find the nearest two numbers of a custom function
body: <p>Given a number, how can I find the nearest two numbers which starts with 1, 2.5 or 5? (10, 25, 50, 100, 250, 500, 1000...endless)</p>
  
  <p>The result should be the nearest nearest higher number, and one below it.</p>
  
  <p>For example: the number 420 should return 250 and 500.
  For example: the number 10 should return 10 and 25.</p>
  
  <p>Can use Lodash if it's helpful.</p>
  
  <p>Thanks.</p>