“For because of this you also pay taxes, for the authorities are ministers of God, attending to this very thing.” -Romans 13:6
The demonstrative pronoun this is neuter and likely refers to the whole of what Paul is saying, namely that rulers are ministers of God executing judgment on evildoers so you should obey them as having been appointed by God. Although, it could be referring more specifically to the clause, for the sake of conscience. Either way, it amounts to the same thing generally speaking: the reason believers should not begrudge paying taxes is because they are raised to support the execution of the ruler’s duties. Taxes are necessary in order to create and maintain the conditions that allow for ordinary, normal life.
And the authorities that collect the taxes are also ministers of God attending to this very work, so they should be respected as well.
There are at least a few important implications to take away from all this. First, taxes are affirmed by God, and therefore should be considered normal and appropriate. Second, the fact that Paul address taxes and tax collectors here shows the context for his exhortation concerning the normal and expected functions of government. Finally, what Paul does not suggest is that every conceivable, despotic act imposed by rulers or authorities is approved by God and therefore should be automatically obeyed.
But in the normal function of things, rulers have authority to administer justice against evil doers. Christians should, therefore, be in subjection to lawful authorities and should pay their taxes in support of the work they are doing.