Macro lens for nikon d3100?

What is the best macro lens to get for a nikon d3100? I already have a 18-55mm and a 55-300 zoom lens, so what can i buy that can get as close up as possible?

The best all around Macro lens for your camera is probably the Nikon AF-S 105mm micro lens.
But that lens costs more than your camera. For a decent inexpensive lens, look at the Nikon AF-S 40mm micro.

Optimized image quality for Digital SLR cameras. Floating Internal Focusing (FIF) system minimizes the aberration in entire focusing range. Super Multi Layer (SML) coating reduces the ghost caused by reflections from the surface of digital image sensors. Minimum aperture of F/32 provides greater depth of field A screw-in hood for convenient use of circular polarizing filters MACRO 50mm F2.8 EX DG incorporates the very latest optical technology and is an ideal standard lens for digital SLR cameras. The new advanced lens design corrects various aberrations.