JSFiddle - React, Tailwind, and code Playground

HTML

<table border="0" cellpadding="0" cellspacing="0">
  <thead>
    <tr>
      <th>1</th>
      <th>2</th>
      <th>3</th>
      <th>4</th>
    </tr>
  </thead>
    <tr>
      <td>1</td>
      <td>1</td>
      <td>1</td>
      <td>1</td>
    </tr>
    <tr>
      <td>1</td>
      <td>1</td>
      <td>1</td>
      <td>1</td>
    </tr>
</table>

CSS

table {
    width:100%;
    text-align:center;
}
table  thead th {
  border-top: 3px solid black;
  border-bottom: 3px solid black;
}
table  thead th:first-child {
  border-left: 3px solid black;
  
  
  border-radius: 4px 0 0 4px;
}

table  thead th:last-child {
  border-right: 3px solid black;
  border-radius: 0 4px 4px 0;
}