After reading blog post of CSS Guy about one pixel rounded corners at Google Analytics web site which is done by using some additional <b> tags I realize that I was using this technique long time ago, but without additional elements. Here is the HTML code:
<ul><li><a href="#">One</a></li><li><a href="#">Two</a></li><li><a href="#">Three</a></li></ul>
And here is the CSS:
ul {padding: 0;margin: 0;width: 20%;}li {background: #000;border-bottom: solid 1px #ccc;border-top: solid 1px #ccc;list-style: none;margin: .3em;padding: 0 1px;position: relative;}li a {background: #e5e5e5;border-bottom: solid 1px #000;border-top: solid 1px #000;display: block;margin: -1px 0;padding: .2em;}
Demo is here.