title: Regular expression for single place decimal number with either 0 or 5
body: <p>What is the regular expression for a decimal number with only one decimal place and either 0 or 5 (whole number of half) and no other. </p>
  
  <p>e.g. <strong>1.0, 3.5, 10.5</strong> and not <strong>1.2, 3.7</strong> e.t.c.</p>
  
  <p>Thank you.</p>