JSFiddle - React, Tailwind, and code Playground

HTML

<div data-table-id="1" class="singleUnitCubic">12.600</div>
<div data-table-id="1" class="singleUnitCubic">4.000</div>
<div>Total: <span data-table-id="1" class="totalCubic"></span></div>

<br>

<div data-table-id="40589" class="singleUnitCubic">19.600</div>
<div data-table-id="40589" class="singleUnitCubic">5.000</div>
<div>Total: <span data-table-id="40589" class="totalCubic"></span></div>

<br>

<div data-table-id="dogs" class="singleUnitCubic">36.600</div>
<div data-table-id="dogs" class="singleUnitCubic">4000.000</div>
<div>Total: <span data-table-id="dogs" class="totalCubic"></span></div>

JavaScript

var totalCubics = document.querySelectorAll('.totalCubic')

totalCubics.forEach((total) => {
  const id = total.getAttribute('data-table-id')
  const units = document.querySelectorAll('div[data-table-id="' + id +'"]');
  console.log(units);

  let sum = 0;
  units.forEach((unit) => {
    sum += parseFloat(unit.textContent)
  });

  total.textContent = sum
});