I’ve done this with a list of products for a one page order form as follows:
1) Each product was created as a check box with the price added in the “Checked Calculation Value” field.
2) I add a Number field next to the product for the user to enter the quantity.
3) Repeat the above for multiple products if required.
Note; the above do NOT have the “include in the auto total” checked.
4) Create a Subtotal field, select the calculation method as “Use an equation” and enter an equation such as:
(field_1 * field_2) + (field_3 * filed_4) + (filed_5 * field_6)
where field_1 is the product ID and field_2 is the quantity ID.
Select the “include in the auto total” checkbox.
5) I added a list field for selecting a shipping option/prices, with “include in the auto total” checked.
5) Finally I added a Total field and which automatically added the subtotal and shipping for the order total.
Hope that makes sense?