I would say yes taxes fund federal spending. I believe this to be true because they take it out of my tax payments. If they had no use of my tax payments why would they take them?
- create a demand for the US dollar
- reduce aggregate demand when needed
- control inflation when needed
It's policy, not operational these days..
Here, try to see it this way:
Dollars enter the economy when the government spends, taxes remove this money.
If you pay taxes with physical dollars, old and dirty bills go into a literal shredder.
The govt will still mark down that your taxes are paid in a computer though.
If the bills are reusable, they might send it out again. Do you consider this spending? Read my FICA post by the way, you'll find it interesting.
(This is a paper money example.)
These days, Most of this happens with a computer between banks and the fed. Paper bills are becoming less relevant, from what I've seen.