This is actually a question that stems from some information that I found when reading this article. The article claims that Mormon Mission Presidents receive each a lot of tax free benefits, and it says the following:
Unlike other church members, this family can receive temple recommends without paying tithing on “income.”
So I looked up what the "temple recommends" are and based on this article and this article, it seems that it is a paper slip that allows a person to enter the temple (both of these articles briefly mention tithing as one of the requirements receiving the "temple recommends").
Anyway I did also find this SE question which has some answers according to which the only consequences from non-tithing are the loss of temple access and participation in some "important saving ordinances".
One of the articles referenced in an answer to that question is this First Presidency Message "Concerning Tithing" (By President Marion G. Romney, dated June 1980). This article says among other things:
Tithing is not a free-will offering; it is a debt, payment of which brings great blessings...it is apparent that tithing is a debt which everyone owes to the Lord as rent for using the things that the Lord has made and given to him to use. The Lord, to whom one owes tithing, is in a position of a preferred creditor. If there is not enough to pay all creditors, he should be paid first.
So this question is about these "important saving ordinances". Does all of this mean that a Mormon who does not pay tithes cannot visit the temple and consequently will not be able to reach salvation?
Note: I am looking for an official opinion by the Mormon Church on this matter. If the official opinion is indeed that "Anyone can attain salvation. Anyone can be denied salvation. It's all up to Our Lord." then that is fine, although it begs the question why anyone would spend their time or money to support this or any other religious organization.