round_half_up() fails to round up for certain decimals (precision issue)

[sfirke]

From the StackOverflow post where I found this function, someone pointed out a bug in June:

There are numerical precision issues, e.g., round2(2436.845, 2) returns 2436.84. Changing z + 0.5 to z + 0.5 + sqrt(.Machine$double.eps) seems to work for me

Indeed, round_half_up(2436.845, 2) yields 2436.84. This function should probably have the same fix implemented, along with a test.