259,345,278 = 259,345,278.00000
I know it's all 0's after the decimal, but let's write it like this just for now: 259,345,278.abcde
(that's so we can tell the difference between which 0 we're talking about)
The 0 sitting on the d is in the ten thousandths place. The next digit over is 0, which is less than 5, so the 0 in the ten thousandths place doesn't round up.
Answer: 259,345,278.abcd = 259,345,278.0000 = 259,345,278
259,345,278 is already rounded to the nearest ten thousandth.