Increasing the width of button by a few percent on hover

So, I have this made.

HTML

<div id="navholder" class="bgd">
<nav id="nav">
    <ul>
        <li><a href="">Почетна</a></li>
        <li><a href="">Делатност</a></li>
        <li><a href="">Историјат</a></li>
        <li><a href="">Службе</a></li>
        <li><a href="">Колектив</a></li>
        <li><a href="">Контакт</a></li>
    </ul>
</nav>
</div>

#navholder {
height: 60px;
text-align: center;
margin: 0 auto;
    }

#nav {
height: 30px;
margin-top: 10px;
background: #B8860B;
    }

#nav ul li{
margin-top: 3px;
display: inline;
font-size: 120%;
opacity: 1.0;
    }

#nav ul li a {
display: inline-block;
height: 120%;
padding: 5px;
-webkit-box-shadow: -1px 0px 22px rgba(50, 50, 50, 0.5);
-moz-box-shadow:    -1px 0px 22px rgba(50, 50, 50, 0.5);
box-shadow:         -1px 0px 22px rgba(50, 50, 50, 0.5);
border: 1px solid white;    
opacity: 1.0;
background: #DAA520;

    }

#nav a:hover {
color: white;
background: black;
width: ?
    }

I want the buttons once hovered over with a mouse to increase about 20%. The problem that I found is if I use the exact width like "width: 60px not every button is of the same size.

On the other hand if I use width: 120% I believe the page takes the width of the whole #navholder element which is defined by the class .bgd.

Any ideas on how can I make this happen?

Thanks.