JSFiddle - React, Tailwind, and code Playground

HTML

<input name="pr-price[]" type="text" class="ad-money ad-price-item" placeholder="price">
<input name="pr-price[]" type="text" class="ad-money ad-price-item" placeholder="price">
<input name="pr-price[]" type="text" class="ad-money ad-price-item" placeholder="price">
<input name="pr-sum" type="text" class="uk-form-width-large ad-money ad-sum-a" value="0">
<input name="pr-discount" type="text" class="uk-form-width-large ad-money ad-discount" value="0">
<input id="ctax" type="checkbox">
<label for="ctax">check to count tax</label>
<input name="pr-tax" type="text" class="uk-form-width-large ad-money ad-tax" value="0">
<input name="pr-finalsum" type="text" class="uk-form-width-large ad-money ad-finalsum" value="0">

JavaScript

$(document).on("change", ".ad-money", function () {
    var sum = 0;
    $(".ad-price-item").each(function () {
        sum += +$(this).val();
    });
    $(".ad-sum-a").val(sum);
    var sumb = 0;
    sumb = sum - $(".ad-discount").val();
    var sumc = 0;
    tax = 0.2;
    if ($("#ctax").is(":checked")) {
        sumc = sum * (1.00 + tax) - sum
    } else {
        sumc = 0;
    }
    sumcround = Math.round(sumc);
    $(".ad-tax").val(sumcround);
    var sumfinal = 0;
    sumfinal = sumb + sumcround;
    $(".ad-finalsum").val(sumfinal);
});