Edit in JSFiddle

<table>
    <tr>
        <td>test</td>
        <td>test</td>
    </tr>
</table>
<table>
    <tr>
        <td>test</td>
        <td>test</td>
    </tr>
</table>
table{
    border-top: 1px solid #000000;
    border-left: 1px solid #000000;
    border-spacing: 0;
    margin-bottom: 5px;
    margin-left: auto;/*ポイント01*/
    margin-right: auto;/*ポイント01*/
}
td{
    padding: 0 3px 3px 3px;
    border-right: 1px solid #000000;
    border-bottom: 1px solid #000000;
}