Google Tag Manager

Add the tag through Google Tag Manager, as a Custom HTML tag.

Not every tag manager keeps a script tag’s attributes as you wrote them (Google Tag Manager strips the data- ones), so add the tag with a few lines of script instead, with your domain in place of example.com:

<script>
(function () {
  var tag = document.createElement('script');
  tag.async = true;
  tag.setAttribute('data-domain', 'example.com');
  tag.src = 'https://fiveb.ar/js/tally.js';
  document.head.appendChild(tag);
})();
</script>

In your container, add a Custom HTML tag holding the script, set it to fire on All Pages, save, then submit and publish the container. See Tag Manager’s help on custom tags.

Once it’s live, check it works.