Thanks for the input thus far, everyone. I appreciate it.
In addition to wondering how common it was to have "odd" billing amounts, I wondered if there were any "issues" to be aware this way. (as opposed to $5 increments)
I'm going to double check my mowing times on each property for the remainder of the season to see how they compare to early on and start evaluating which jobs need to be adjusted for next season.
Everyone seems happy with my work, so I'm confident that the majority will not balk over a $2/$3, or in some cases, even a $5 increase.