When you sell someone product wholesale (like soap to a store for resale), you must have them fill out a 'Resale Tax Certificate' that you keep on file. Then, you don't need to charge them tax. The company filling out the form must be a licensed business in order to not be charged tax:
http://www.growing4you.com/downloads/pa ... ficate.pdf (PA resale certificate download)
When you are selling the soap to another person in a craft show type situation, yes, you must collect tax, keep track of it and give it to the State along with whatever forms they want you to have.