actually, this is not a bug and it is pretty common. its called a floating point “error” and in a nutshell, it has to do things with how decimal numbers are stored within a google sheets (even excel or any other app)
more details can be found here: https://en.wikipedia.org/wiki/IEEE_754
to counter it you will need to introduce rounding like:
=ROUND(SUM(A1:A))
this is not an ideal solution for all cases so depending on your requirements you may need to use these instead of ROUND
:
ROUNDUP
ROUNDDOWN
TRUNC
TEXT