ruby-on-rails - The totals of the cart item amounts do not match order amounts. error with paypal express gem in rails

Question

I have used gem 'paypal-express' for connecting paypal from rails 4 application.

I have added to

item = {
                               name: self.title,
                               description: self.title,
                               quantity: self.quantity,
                               item_number: self.item_number,
                               amount: self.amount
                           }

as a payment request.. For multiple number of items it is always showing the following error.. The totals of the cart item amounts do not match order amounts

I have rounded off the value to 2 decimal places.. But it still shows error ... Is there any way to fix it?

Thanks