Tariff Help

My father ordered something which I just figured out is coming from China and already shipped. It's one item at $15. I have no idea how the tariffs work, does anyone know what he will be charged and how tariff is collected? Can my father refuse the tariff by refusing the package? I'm so angry that Amazon does not make it clear when purchasing that an item is being shipped from China or where...I only found out by using a website and entering the parcel info after it had already been shipped. My friend had told me a month ago that she was unable to order something and Amazon stated the item was from China and they would not let her buy it....so I thought Amazon was making it clear for consumers based off that info...well I guess NOT.