nj tax on service fees?

What is the name of your state? NJ

I purchased cosmetics from well known door-to-door company and noticed that a 50cent "service charge" was separately added to the merchandise total and then 6% sales tax calculated on the grand total.

Although this is a small amount we are talking about, I wanted to know if it is correct to calculate the sales tax on the grand total (merchandise plus service charge) , rather than just on the merchandise purchased?

Their Company website mentions that in only 4 states including NJ, tax is calculated only on the merchandise, then shipping and handling is added. Tax is collected on the grand total in all other states. Although the salesperson said that the service charge is to recoup a shipping charge she must pay the Company, the Company says it is a "processing fee" and must be taxed.

We'll I'm sure confused...any suggestions?
Thanks
Joe/NJ