Hello and welcome aboard
If you are looking to make tabs or fingers fit tightly you have to include the width of the cut made by the laser in your calculations. Normally that is 0.005 inches. In Inkscape, you can set the line thickness to 0.005 inches and use Path > Stroke to Path that will create 2 lines on either side of that thickness so it will be exactly half the width of the cut when you just delete the inner line. You might want to try making some joints with scraps till you get exactly what you want.
For myself, I usually want to apply a discreet amount of wood glue so stuff does not come apart even when the fit is very tight, The exception is something like a hinge that may break and need replacement.