JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div class="div content">
    <div class="categories">
      <div class="categories_item">
        <a href="" class="">
          <span>Item</span>
        </a>
      </div>
      <div class="categories_item">
        <a href="" class="">
          <span>Item</span>
        </a>
      </div>
      <div class="categories_item">
        <a href="" class="">
          <span>Item</span>
        </a>
      </div>
      <div class="categories_item">
        <a href="" class="">
          <span>Item</span>
        </a>
      </div>
      <div class="categories_item">
        <a href="" class="">
          <span>Item</span>
        </a>
      </div>
      <div class="categories_item">
        <a href="" class="">
          <span>Item</span>
        </a>
      </div>
      <div class="categories_item">
        <a href="" class="">
          <span>Item</span>
        </a>
      </div>
      <div class="categories_item">
        <a href="" class="">
          <span>Item</span>
        </a>
      </div>
      <div class="categories_item">
        <a href="" class="">
          <span>Item</span>
        </a>
      </div>
      <div class="categories_item">
        <a href="" class="">
          <span>Item</span>
        </a>
      </div>
      <div class="categories_item">
        <a href="" class="">
          <span>Item</span>
        </a>
      </div>
      <div class="categories_item">
        <a href="" class="">
          <span>Item</span>
        </a>
      </div>
    </div>
  </div>
</div>

CSS

*,
*:after,
*:before {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

.container {
  float: left;
  width: 100%;
  background-color: red;
}

.content {
  width: 94%;
  margin: 0px auto;
  background-color: yellow;
  padding: 30px;
}

.categories {
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;                /* NEW */
}

.categories_item a {
  color: white;
}

.categories_item {
  flex: 1 0 20%;                 /* NEW */
  margin: 5px;                   /* NEW */
  background-color: blue;
}