In many of these everyday phrases, a word-by-word translation wouldn't do us any good since that would produce a result that sounds unnatural in either language. That is why you'll find that the words here don't match up by themselves. The phrase is translated, not the individual words.
"tack" means "thank you". however, you could ask for something and say "pastan med köttbullar, tack". i'm not sure how common this is for a native swedish speaker to say though.
it's like ordering in a restaurant and saying thank you instead of please, because you know they're not going to say "no". it's fairly common here in the south USA, but i'm not sure about other english speaking countries/regions.