I downloaded a free plugin that allows for you to add a custom handling fee at the product level, and then it appears in the calculation breakdown in the shopping cart/checkout.
Fatal flaw is that (I think) the handling_fee field wasn't assigned an appropriate data type to account for any values to the right of the decimal point, because when you enter 5.50 for handling on the product page, only "5.00" appears in the shopping cart.
I have the php file open and I'm tinkering around in it. I've changed the input type from text to number, and added step "0.01", but that's not affecting how the value appears in the shopping cart.
It's the 'WooCommerce Dynamic Handling' plugin.
Any ideas?