Problem with calculation of product price by "decimal" length

<?php
jimport('joomla.plugin.plugin');

class plgSystemCustom_quantity extends JPlugin{
}

if(!function_exists('fid_custom_quantity_normalize_length')) {
	function fid_custom_quantity_normalize_length($value) {
		$value = trim((string) $value);
		$value = str_replace(',', '.', $value);
		return (float) $value;
	}
}

if(!function_exists('hikashop_product_price_for_quantity_in_cart') && !function_exists('hikashop_product_price_for_quantity_in_order')) {

	function hikashop_product_price_for_quantity_in_cart(&$product){
	$currencyClass = hikashop_get('class.currency');

	$quantity = @$product->cart_product_quantity;
	$ordered_length = 1;

	if(!empty($product->ordered_length)){
		$ordered_length = fid_custom_quantity_normalize_length($product->ordered_length);
	}

	$currencyClass->quantityPrices($product->prices, $quantity, $product->cart_product_total_quantity);

	if($ordered_length > 0 && $ordered_length != 1 && !empty($product->prices)) {
		foreach($product->prices as $k => $price) {
			if(isset($price->price_value)) {
				$product->prices[$k]->price_value = (float) $price->price_value * $ordered_length;
			}

			if(isset($price->price_value_with_tax)) {
				$product->prices[$k]->price_value_with_tax = (float) $price->price_value_with_tax * $ordered_length;
			}
		}
	}
}

	function hikashop_product_price_for_quantity_in_order(&$product){
		$quantity = $product->order_product_quantity;

		if(!empty($product->ordered_length)){
			$ordered_length = fid_custom_quantity_normalize_length($product->ordered_length);
			$quantity = $quantity * $ordered_length;
		}

		$product->order_product_total_price_no_vat = $product->order_product_price * $quantity;
		$product->order_product_total_price = ($product->order_product_price + $product->order_product_tax) * $quantity;
	}
}