“Cowboys can never be accountants because all they do is round up”

A cowboy riddle has been cited in print since at least the early 2010s:
 
Q: Why aren’t cowboys good at math?
A: Because they always round up!

   
“Cowboys can never be accountants because all they do is round up” was posted on Twitter on November 18, 2015.
 
     
BIGScience (Kamloops, BC)
October 2010
Pg. 2:
Riddle
Why do cowboys not use decimal numbers?
Answer: Because they always ‘round up’.
     
Twitter
Bella Rivera‏
@bellariv
Why aren’t cowboys good at math?
They always round up! 🐎✖️➗ #badjokes
1:05 PM - 1 Feb 2015
 
Twitter
Luke Newquist‏
@LukeNewquist
Cowboys can never be accountants because all they do is round up.
7:40 PM - 18 Nov 2015
     
Hampton Union (Portsmouth, NH)
Fundraiser to benefit Hampton Academy student battling cancer
By Liz Premo / .(JavaScript must be enabled to view this email address)
Posted May 19, 2016 at 6:14 PM
Updated May 19, 2016 at 6:14 PM
(...)
(Example: Why are cowboys bad at math? Because they always round UP!)
   
Twitter
Dave‏
@gneicco
Q. Why do cowboys get into tax trouble with the IRS?
A. Because they always round up.
1:51 PM - 11 Jul 2016
 
Reddit—Jokes
Why are cowboys bad at being accountants?
submitted August 6, 2017 by DrBubs
Because they always round up.