tally vs add together

tally is a noun but add together is not a noun.

Word	Noun	Adjective	Verb	Adverb
tally	Yes	No	Yes	No
add together	No	No	Yes	No

As verbs, tally and add together are synonyms defined as:

Other synonyms of tally include add, add up, sum, sum up, summate, tot, tot up, total, tote up.

tally (noun)	add together (noun)
the act of counting; reciting numbers in ascending order
a score in baseball made by a runner touching all four bases safely
a bill for an amount due

tally (verb)	add together (verb)
determine the sum of	make an addition by combining numbers
keep score, as in games	determine the sum of
gain points in a game
be compatible, similar or consistent; coincide in their characteristics