Floating point type to store numbers

Hi,
I am currently using Postgresql to maintain an application which is used
for trading and back office operations. Currently our monetary fields are
stored in Varchar. I am finding a huge CPU utilization while converting
from varchar to float. I think for reasons unknown to me, we originally
stored $ amounts and rates in varchar. I am planning to convert our tables
that hold money fields and rates from varchar to float. I do not want to
convert to numeric because numeric is a special string type.

The question is: how accurate is floating point numbers in Postgres. We
are using 7.4 soon to be moving to 8.2.
I need the accuracy to about 6 decimal points. I have read that floating
points can convert to numbers in accurately.

Thank you.
Radhika

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