If you would prefer to set shipping calculation as flat rates based on order total, you can do that using our Shipping Rules feature. In this case, weights and package types would not matter, so you can just leave what you've set up for each product as it is.
Go to Seller Admin > Cart Shipping Settings and set up the following:
Shipping Origin: select your country and enter your zipcode (if you're outside the US, just enter any 5-digit number);
Shipping Destinations: if you will only ship to certain countries, select them in the list, or otherwise select nothing for Worldwide shipping;
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: 5.95
Country: Select your country;
Max. Item Total: 20.00
Click Submit to save the Rule.
Next Domestic Rule:
Shipping Rate Calculator: Flat
Shipping Amount: 6.95
Country: Select your country;
Min. Item Total: 20.01
Max. Item Total: 45.00
Click Submit to save the Rule.
Continue creating Rules for other order-total thresholds. For your top rule, you can just leave the Max. Item Total blank (or 0, same effect) to have no maximum threshold.
If you will ship Internationally at different rates:
Shipping Rate Calculator: Flat
Shipping Amount: [your lowest int'l flat rate here]
Country: All Countries (i.e., rest of the world, covers all countries you'd selected in the Shipping Destinations list which don't have Rules of their own);
Max. Item Total: 20.00
Click Submit to save the Rule.
Continue creating Rules for Int'l destinations at other order total thresholds.
Click Back to Admin, and you're done!
