If you're only shipping within the US, it's simplest to set up a flat $1 per item with a one-time Handling fee of $5.50 added to the shipping charges for each shippable order:
Go to Seller Admin > View/Edit/Delete Products:
Select an existing shippable product of yours and click Edit;
On the first screen, if Shipping/Buyer's Address is not checked there, tick that box;
Click Next until you can Submit to save settings (Shipping Options will not matter);
Repeat this for all your tangible goods;
When adding new shippable products, remember to enable Shipping/Buyer's Address.
Go to Seller Admin > Cart Shipping Settings and set up the following:
Shipping Origin: select United States and enter your zipcode;
Shipping Destinations: select United States;
Leave all other settings blank or 0.00;
Click Next to save settings and proceed to the Shipping Rules screen.
In the Existing Shipping Rules menu, select and Delete any Rules you may have saved there.
Set up your first Shipping Rule for Domestic shipping:
Shipping Rate Calculator: Flat;
Shipping Amount: 1.00;
Country: United States;
Click Submit to save the Rule.
Click Back to Admin, and you're done!