Objects after too wide after printing

Hi!
I have a prusa i3 with JHeadV header (0.5mm diameter), with Rumba driver, with heated bed mk2a.
Previously I was using the Cura slicer, but it lacked web interface, so I swithced to Octoprint and Slic3r.

Both solutions were great, but also impacted with one major issue. The printed objects are too wide (~0.1mm too wide).
It makes no problem with those big blocks I'm using in my projects, but the smaller prints and gears are unusable.

Any advices on how to set up everything correctly? It seems, that the printers extruder's external path should be tapered, but I don't have any idea how achieve that.

Thank you in advance!

What is the results when you printed a 20mm cube? if it's off then it should be your steps/mm value, if not, probably you should opt in for smaller nozzle

Or reduce your extruder multiplier or steps/mm.