Please don't force users to round values, it is a bad practice.
Use proper testing of floating point numbers instead.
In this case there is even some ambiguity on where to use rounding (taking the square root can produce non-rational numbers)

I think a good rule for rounding is to use it only to display values with a reasonable number of digits.

Rounding values without apparent need is considered bad practice.
I assume that these challenges have educational relevance for many participants.

My suggestion: drop the requirement to round the results and use proper testing methods instead

Parameter naming is wrong, should be "message" instead of "greetings"
Also the function should be called "contains_greetings"

This is clever but definitely not best practice

The note about single digit numbers being automorphic should be removed, as it is contradicted by tests as well as mathematical definition