I have a table:

create table payments
(
    id serial constraint payments_pkey primary key,
    amount real not null
);

There are some data:

amount
79740.03
4430.64
95429.1
1567.73
206959.31

I need to sum amount. For that I use sum:

select sum(payments.amount)
from payments

It gives me 388126.8 but I expect 388126.81.

But if I execute query with casting:

select sum(cast(cast(payments.amount as text) as decimal))
from payments

then it gives me expected sum 388126.81.

What’s wrong with first query?