JSFiddle - React, Tailwind, and code Playground

HTML

<table border="1px">
  <thead>
    <tr class="first">
        <td rowspan="2">Item No</td>
        <th colspan="2">Store ABC</th>
        <th colspan="2">Store DEF</th>
    </tr>
    <tr class="second">
        <th>Baskets</th>
        <th>Customers</th>
        <th>Baskets</th>
        <th>Customers</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
      <td>345</td>
      <td>345</td>
      <td>345</td>
    </tr>
    <tr>
      <th>123</th>
      <td>345</td>
     ...

CSS

table {
  height: 100%;
  border-collapse: collapse;
  width: 100%;
  margin: 10px;
  font-size: 0.8em;
}

thead tr.first th, thead tr.first td {
  position: sticky;
  top: 0;
  background: #eee;
}

thead tr.second th, thead tr.second td {
  position: sticky;
  top: 17px;
  background: #eee;
}