Hello Vaclav,
Thanks for your feedback, I just made a fix regarding that issue, so can you edit your file "administrator\components\com_hikashop\helpers\helper.php" and change these lines :
if(@$method->payment_params->payment_price_use_tax) {
	if(isset($order->order_full_price))
		$price = $order->order_full_price;
	if(isset($order->total->prices[0]->price_value_with_tax))
		$price = $order->total->prices[0]->price_value_with_tax;
	if(isset($order->full_total->prices[0]->price_value_with_tax))
		$price = $order->full_total->prices[0]->price_value_with_tax;
} else {
	if(isset($order->order_full_price))
		$price = $order->order_full_price;
	if(isset($order->total->prices[0]->price_value))
		$price = $order->total->prices[0]->price_value;
	if(isset($order->full_total->prices[0]->price_value))
		$price = $order->full_total->prices[0]->price_value;
}By :
if(@$method->payment_params->payment_price_use_tax) {
	if(isset($order->order_full_price))
		$price = $order->order_full_price;
	if(isset($order->total->prices[0]->price_value_with_tax))
		$price = $order->total->prices[0]->price_value_with_tax;
	if(isset($order->full_total->prices[0]->price_value_with_tax))
		$price = $order->full_total->prices[0]->price_value_with_tax;
	if(isset($order->full_total->prices[0]->price_value_without_payment_with_tax))
		$price = $order->full_total->prices[0]->price_value_without_payment_with_tax;
} else {
	if(isset($order->order_full_price))
		$price = $order->order_full_price;
	if(isset($order->total->prices[0]->price_value))
		$price = $order->total->prices[0]->price_value;
	if(isset($order->full_total->prices[0]->price_value))
		$price = $order->full_total->prices[0]->price_value;
	if(isset($order->full_total->prices[0]->price_value_without_payment))
		$price = $order->full_total->prices[0]->price_value_without_payment;
}