round( reset( WC_Tax::get_rates() )['rate'] )

// Function to add shortcode to display tax rates
function woocommerce_template_display_tax() {
global $product;
$tax_rates = WC_Tax::get_rates( $product->get_tax_class() );
if (!empty($tax_rates)) {
    $tax_rate = reset($tax_rates);
    echo sprintf(_x('Price without %.2f %% tax', 'Text for tax rate. %.2f =
    tax rate', 'wptheme.foundation'), $tax_rate['rate']);
    }
 }
add_shortcode('display_tax', 'woocommerce_template_display_tax');