Floating multiple li's left and right

Question

I am trying to make a custom sidebar in wordpress, i have all the element and info in li's, what i am trying to do is try to shift the half of the total li's to left and half to the right...

What i am using is float/clear left and right, that not seems to work as i wanted...

HTML Structure:-

<ul>
    <li class="left">Left</li>
    <li class="left">Left</li>
    <li class="left">Left</li>
    <li class="left">Left</li>
    <li class="left">Left</li>
    <li class="right">Right</li>
    <li class="right">Right</li>
    <li class="right">Right</li>
    <li class="right">Right</li>
    <li class="right">Right</li>
</ul>

The CSS:-

.left { float:left; width:50%; clear:left; }
.right { float:right; width:50%; clear:right }

jsFiddle

Answer 1

Done it with simple markup and styles http://codepen.io/ruinunes/pen/bpgpZV

HAML:

%ul.chat
  %li.stamp 
    Saturday
    %span 20:32
  %li.left Who is it?
  %li.right It's Little Nero's, sir. I have your pizza.
  %li.left Leave it on the doorstep and get the hell outta here
  %li.stamp 
    Saturday
    %span 20:33
  %li.right Okay, but what about the money?
  %li.left What money?
  %li.right Well, you have to pay for your pizza, sir.
  %li.left Is that a fact? How much do I owe you?
  %li.left Keep the change, ya filthy animal!
  %li.right Cheapskate.

SCSS

ul.chat {
  font-family: sans-serif;
  list-style:none;
  margin: 0 auto;
  padding: 0;
  width: 50%;

  li {
    margin-bottom: 10px;
    display: inline-block;
    border-radius: 8px;
    padding: 10px;

    &.left { 
      background: #e3e3e3;
      float:left;
      margin-right: 50%;
      width:50%;
      border-top-left-radius: 0;
    }

    &.right {
      background: #6CCE66;
      color: #fff;
      float: right;
      width: 50%;
      border-top-right-radius: 0;
    }

    &.stamp {
      color: #666;
      font-size: 80%;
      text-align: center;
      width: 100%;
      span {
        color: #999;
      }
    }
  }

}