The way that Rome ruled was a little different than the constructs that we think of today as government. Rome preferred a fairly small government for how large their civilization was. I would go as far to say that their army was the largest part of their whole government at any time, so what would that mean for tax collecting?

When you watch movies of Jesus there is always a scene about a tax collector knocking on the door of some poor person's house with two big burly Roman soldiers. Is this accurate? I would say no. Tax collecting was actually a contract business. Rome would put out a contact saying "we want someone who can collect 100,000$ from this community." Then, tax collectors would bid saying "I can get you 150,000$" and who ever pretty much said the highest amount would get the contract.

Then it was the tax collectors job to get whatever he said he could get for Rome, but remember, tax collectors want more than just money for Rome. They want to pay themselves as well. So they would go and collect as much money as they could and pay Rome and keep the rest. So taxes were as much as a person could get, and it was always out of whole communities rather than individuals. The Roman military would have had little to do with any tax collecting in most circumstances.

As for what the tax went to? Military spending(hard to explain this) and infrastructure almost exclusively. Almost every office that was held was unpaid.

Edit: I do want to say that I don't really believe the whole Jesus thing, but this would have been a general Roman tax collecting.