JMNT(i)
16 And so, they sent off their disciples with the Herodians (supporters and members of the political associates of Herod) on a mission to Him, as a group, saying, "Teacher, we have seen and now know that you are genuine and honest (truthful; trustworthy; dependable; true), and further, you habitually teach God's way (path; road) in truth and reality. Furthermore, it is not normally a concern or worry to you about anyone, for you are not constantly looking into peoples' faces [to see their reaction] or observing their outward appearance [to take into account their social position].
17 "Tell us, then, how it normally seeming to you (= what are you now thinking of this situation; What is your opinion): Is it normally allowed by [our] custom and Law to give (= pay) a poll (or: census) tax to Caesar (the Roman emperor), or not?"
18 But Jesus, knowing by intimate experience their worthlessness (their poor character and wicked intent), says, "Why are you men constantly examining and testing Me, you people who make close inspection of the writings so as to be opinionated and hyper-critical, having all the answers (see 6:2, above)?