score:2
Good question.
One answer could be that tithing is shown before the Law of Moses between Abram and Melchizedek.
And blessed be the most high God, which hath delivered thine enemies into thy hand. And he gave him tithes of all. Gen 14:20
But then, so was the Sabbath wherein God sanctified the seventh day.
And on the seventh day God ended his work which he had made; and he rested on the seventh day from all his work which he had made. And God blessed the seventh day, and sanctified it: because that in it he had rested from all his work which God created and made. Gen 2:2-3
Another answer is that if you don't tithe, you are cursed.
Will a man rob God? Yet ye have robbed me. But ye say, Wherein have we robbed thee? In tithes and offerings. Ye are cursed with a curse: for ye have robbed me, even this whole nation. Malachi 3:8-9
But then if you don't keep the Sabbath, you are likewise cursed.
But it shall come to pass, if thou wilt not hearken unto the voice of the LORD thy God, to observe to do all his commandments and his statutes which I command thee this day; that all these curses shall come upon thee, and overtake thee: Deut 28:15
So, to attempt an answer to the OP, there is no biblical basis to tithe, but not observe the Sabbath.