fixed issue magento#18724 for 2.3-develop

Author: Shubham Sharma

app/code/Magento/Tax/view/frontend/templates/order/tax.phtml

@@ -26,7 +26,7 @@
                 <td <?= /* @escapeNotVerified */ $block->getLabelProperties() ?>>
                     <?= $block->escapeHtml($title) ?>
                     <?php if (!is_null($percent)): ?>
-                        (<?= (float)$percent ?>%)
+                        (<?= /* @escapeNotVerified */ $_order->formatPrice((float)$percent) ?>%)
                     <?php endif; ?>
                     <br />
                 </td>

app/code/Magento/Tax/view/frontend/web/template/checkout/summary/tax.html

@@ -38,7 +38,7 @@
         <!-- ko foreach: rates -->
         <tr class="totals-tax-details">
             <!-- ko if: percent -->
-                <th class="mark" scope="row" data-bind="text: title + ' (' + percent + '%)'"></th>
+                <th class="mark" scope="row" data-bind="text: title + ' (' + $parents[1].formatPrice(percent) + '%)'"></th>
             <!-- /ko -->
             <!-- ko if: !percent -->
                 <th class="mark" scope="row" data-bind="text: title"></th>