title: python np.round() with decimal option larger than 2
body: <p>Python has default round() function, but I was programming with cython and want to replace pythonic code with numpy function. However, I got the following results when experimenting it in terminal.</p>
  
  <pre><code>&gt;&gt;&gt; np.around(1.23456789)
  1.0
  &gt;&gt;&gt; np.around(1.23456789, decimals=0)
  1.0
  &gt;&gt;&gt; np.around(1.23456789, decimals=1)
  1.2
  &gt;&gt;&gt; np.around(1.23456789, decimals=2)
  1.23
  &gt;&gt;&gt; np.around(1.23456789, decimals=3)
  1.2350000000000001
  &gt;&gt;&gt; np.around(1.23456789, decimals=4)
  1.2345999999999999
  </code></pre>
  
  <p>Which is kind of strange, and I still want the following "desired" result:</p>
  
  <pre><code>&gt;&gt;&gt; round(1.23456789,3)
  1.235
  &gt;&gt;&gt; round(1.23456789,4)
  1.2346
  </code></pre>