LTSpice Transient Analysis - How to specify the number of data points per step
In general, SPICE uses an adaptive step-size in transient simulations to minimize simulation time while maintaining accuracy. When circuit variables (node voltages, for example) are changing rapidly, it will take shorter time steps, and when circuit variables are changing slowly, it will take longer time steps.

You can specify a "maximum timestep" in case you want to override the built-in algorithm (either because you find the built-in algorithm doesn't give accurate results or to produce denser points for plotting). In your case, specifying a maximum of maybe 0.1 or 0.2 us would likely result in this timestep being used for all your simulation runs, at the cost of longer simulation times. Specify this in the "Edit Simulation Command" dialog.

Alternatively, you could post-process the results to interpolate output values on whatever time intervals you want, or simply do an x vs y plot in Excel instead of the standard y vs category plot.