Hello, I had some slight success.
When using the Table Rate Plug, instead of choosing PER Order in the calculation Type setting, you can choose Calculate Per Row or Calculate Per Class.
This works well for combining diff shipping classes and rows ( i guess a row is a line/row of products in the checkout)
So if someone places a cake and a couple t shirts in the cart, it would return the correct shipping for 2 t-shirts and then the rate for a cake and then combine those costs into a total.
But I now have a new problem. Im actually using the USPS plug-in because all I have to do is enter the dimensions and weight of my products, define which USPS services I want ( Priority MAil in my case) and then at checkout it returns the best rate for the customer. This works great for 90% of my products BUT i want to sell Cakes and Produce, which will need to be overnighted and packed on Ice. Im not sure how i can use my usps plug in along side something like this and then have totals combine?????