The 'round' mathematical function doesn't document which rounding
strategy it uses. If this would be documented then users can rely on its
rounding behavior. For double precision the rounding probably depends on
your platform. For numeric is the function seems to round to nearest
with ties (a 5) going away from zero (sometimes referred to as "round
half up). 6.5 -> 7.0 and -6.5 -> -7.0.
https://www.postgresql.org/docs/current/functions-math.html
Kind regards, Rudolph