How to round a number relatively?

Question

Mathematics

Perhaps the question is closer to fuzzy sets.

10
20
30
50
100
150
200
300
500
700
1000
1250
1500
2000
...
1.000.000
1.050.000
1.100.000

_

Answer 1

=ROUND(A2/10^ROUND(LOG10(A2)*B$1))*10^ROUND(LOG10(A2)*B$1)

Is that enough? The parameter in the top line (0.5..0.85) is "the level of a person's love" :)
PS By the way, F4 has a curious artifact. So 0.85 is too high a level of love.