You'll have better luck with your Tamron 55-200 Macro. You'll be able to focus a lot closer at the 200mm end. It most likely wont be 1:1, probably 1:2 and possibly 1:3 or 1:4, but it will be more than the 18-55mm.
I just recently started getting more into Macro. I used to use a Quantaray 70-300 that had a macro feature at the 300mm but was 1:2 ratio. Earlier this month I got the Tamron 90mm f/2.8 Macro. WOW what a lens. Got it used at keh.com at a very good price and it's in excellent condition. Takes very sharp photos and will focus up to about 3 inches. Only issues is that inside 10' or so of the subject it only opens to about f/3 or f/3.5 which is still pretty wide.
Here's one pic I took as an example:
