INCREMENTS = 1 mm, .5 in, ... - Defines the increments available for incremental jogs. The INCREMENTS can be used to override the default. The values can be decimal numbers (e.g., 0.1000) or fractional numbers (e.g., 1/16), optionally followed by a unit (cm, mm, um, inch, in or mil). If a unit is not specified the machine unit is assumed. Metric and imperial distances may be mixed: INCREMENTS = 1 inch, 1 mil, 1 cm, 1 mm, 1 um is a valid entry.
From the docs. I don't think you can change on the fly since it in the initialization file. I could be wrong, but you can mix and match to suit your needs. I rarely use any besides the fine feed. Could probably get away with 4 units, jog, mm, mm, in, in
