I have run into this issue before and found that sometimes padding is the issue.
By removing padding from the ul, any li's set to inline-block will be nicely centred:
* {_x000D_
box-sizing: border-box;_x000D_
}_x000D_
_x000D_
ul {_x000D_
width: 120px;_x000D_
margin: auto;_x000D_
text-align: center;_x000D_
border: 1px solid black;_x000D_
}_x000D_
_x000D_
li {_x000D_
display: inline-block;_x000D_
}_x000D_
_x000D_
ul.no_pad {_x000D_
padding: 0;_x000D_
}_x000D_
_x000D_
p {_x000D_
margin: auto;_x000D_
text-align: center;_x000D_
}_x000D_
_x000D_
.break {_x000D_
margin: 50px 10px;_x000D_
}
_x000D_
<div> _x000D_
<p>With Padding (Default Style)</p>_x000D_
<ul class="with_pad">_x000D_
<li>x</li>_x000D_
<li>x</li>_x000D_
<li>x</li>_x000D_
<li>x</li>_x000D_
</ul>_x000D_
<div class="break"></div>_x000D_
<p>No Padding (Padding: 0)</p>_x000D_
<ul class="no_pad">_x000D_
<li>x</li>_x000D_
<li>x</li>_x000D_
<li>x</li>_x000D_
<li>x</li>_x000D_
</ul>_x000D_
<div>
_x000D_
Hope that helps anyone running into this same issue :)
Cheers,
Jake