Returns the answer to the question at what point the trailing 1 becomes too small to be worth printing?, or worse, becomes smaller than the precision of floating-point numbers.
The rule is as follows: if we find 000 or 999 in the decimal expansion of a number, then it should be rounded for display. arground(5.3001) and arground(5.2998) return 4, suggesting to keep all 4 digits after the decimal point, but arground(5.30001) and arground(5.29998) return 1, suggesting that to present these numbers as 5.3. Thus, 5.3001 stays 5.3001; 5.30001 would become 5.3; 5.2998 stays 5.2998; 5.29998 becomes 5.3.
show summary "Roundings" a1a3 with
arground(5.3001) as "of 5.3001"
arground(5.30001) as "of 5.30001"
arground(5.29998) as "of 5.29998"