JSFiddle - React, Tailwind, and code Playground
HTML
<input type="checkbox" value="3.99" id="one" checked>
<input type="checkbox" value="5.99" id="two">
<input type="checkbox" value="7.99" id="three">
<div id="total">0</div>
JavaScript
$('input:checkbox').on('change', function () {
if(this.checked)
$('#total').text(parseFloat($('#total').text()) + parseFloat($(this).val()))
}).trigger("change")