Add Custom CSS to Shopping Cart Page

Does anyone know how to add custom css uniquely on the Shopping Cart page? This CSS is used to block an external shopping cart we use for specific products from showing up overlaid on our shopping cart page?

There is no code-injection on the shopping cart page so maybe there is a way to add my CSS to the global custom CSS but point it to the shopping cart page? 

You can wrap CSS code with this class

body#cart {
enter your CSS code here
}