JSFiddle - React, Tailwind, and code Playground

HTML

<table class="IFTAtable" id="FuelTaxIFTA" width="100%" border="1" cellpadding="2.5" cellspacing="5">
  <tr>
    <th>Juristiction</th>
    <th>Rate Code</th>
    <th>Total IFTA Miles by State</th>
    <th>Taxable Miles</th>
    <th>MPG </th>
    <th>Taxable Gallons</th>
    <th>Tax Paid Gallons</th>
    <th>Net Taxable Gallons</th>
    <th>Tax Rate</th>
    <th>Tax Credit or Tax Due</th>
    <th>Interest </th>
    <th>Total Due</th>
  </tr>
  <tr>
    <td>CT</td>
    <td>089</td>
    <td>
      <input type="text" class="CtMiles" /> </td>
    <td>
      <input type="text" name="stateMiles" id="CtMiles" class="CtMiles" />
    </td>
    <td>
      <input id="MPG" type="text" name="mpg" class="mpg">
    </td>
    <td>
      <input type="text" readonly="readonly" class="calcTax[State]" />
    </td>
    <td>
      <input type="text" class="taxPdGallonsCT" onchange="doMath()" tabindex="1" placeholder="TCH RPT" />
    </td>
    <td></td>
    <td>.4170</td>
    <td></td>
    <td>&nbsp;</td>
    <td></td>
  </tr>
  <tr>
    <td>DE</td>
    <td>086</td>
    <td>
      <input type="text" class="DeMiles" readonly="readonly" />
    </td>
    <td>
      <input type="text" name="stateMiles" id="DeMiles" class="DeMiles" readonly="readonly" />
    </td>
    <td>
      <input id="MPG" type="text" name="mpg" class="mpg" readonly="readonly">
    </td>
    <td>
      <input type="text" readonly="readonly" class="calcTax[State]" />
    </td>
    <td>
      <input type="text" class="taxPdGallons[State]" tabindex="2" placeholder="TCH RPT" />
    </td>
    <td>&nbsp;</td>
    <td>.2200</td>
    <td>&nbsp;</td>
    <td>&nbsp;</td>
    <td>&nbsp;</td>
  </tr>
  <tr>
    <td>IN</td>
    <td>179</td>
    <td>
      <input type="text" class="InMiles" readonly="readonly" />
    </td>
    <td>
      <input type="text" name="stateMiles" id="InMiles" class="InMiles" readonly="readonly" />
    </td>
    <td>
      <input id="MPG" type="text" name="mpg" class="mpg" readonly="readonly">
    </td>
   ...

JavaScript

function calcCT() {

  $(document).ready(function() {

    var total = 0;
    $(".CT").each(function() {
      total += parseFloat($(this).text());
    });
    $("#CtMiles").val(Math.round(total));
    doMath(CT);
  });
}

function doMath(this) {
  var miles = $(this).val();
  var mpg = $(this).val();
  var t = miles / mpg;
  var tax = $(this).val(Math.round(t));
};