A minute is 1/60 of a degree so 5 minutes is 1/12 degree resolution.
ETOPO2 is a combination of observations, each with their own errors. Some are ship soundings, some are gravitational from satellites. The gravitational ones are terrible close to land.
Manual? What manual? There is a
SCRUM manual out there which is still useful but very dated. The numerics and many other details have changed, with the numerics being described in a new paper by Haidvogel et al. We have a contract with MMS to produce a draft updated manual by a year from now.
Also, there is an ongoing attempt to make a
ROMS wiki. Contact Dave Robertson if you have things to contribute to it and would like the permission to do so.