rounding in between orders of magnitude

[debrouwere]

Quantize to somewhere in between a magnitude.

For example:

• ceil(55.25, 1.2) => 55.26
• floor(55.25, 1.2) => 55.24
• round(55.3333, 2.5) => 55.335
• round(12.345, 1.1) == round(12.345, 2) == 12.34

Note that quantization beyond an order of magnitude results
in a variable amount of decimal digits depending on the
lowest common multiple.

For example:

• floor(1.2341234, 1.25) == 1.225
• floor(1.2341234, 1.50) == 1.20

[debrouwere]

This kind of quantization is often useful when producing charts: when the maximum value is 117K, the axis should preferably go from 0 to 120K or 0 to 125K instead.

Should support round, ceil, floor, min and max.