I agree with @Joe Facenda. As a Realtor I am aware of the market conditions and I can and will suggest to my client what I believe will actually secure the deal. In Portland we are in a very competitive market and even if my client comes up with a number 5% below asking I will likely advise them to put in their best possible offer. Good investment properties are getting well over list price with multiple offers, sometimes dozens.
Any good Realtor will be in contact with the listing agent and we typically know how many offers are in, approximately what the highest offer is, if other buyers have dropped their inspection contingency, if they are working with cash or hard money loans, etc. I will know how strong the other offers are so I will advise my client accordingly.
If my client decides they want to put in a low offer because that is what their model suggests I will happily do that. I will be very transparent with them though because I do not want them to get discouraged after another rejected offer.
Again, I agree with Joe in that if the number I suggest coming in at is way too high for my client I will suggest that we move on.
No matter what, my goal is to secure the best possible deal for my client. If their deal is profitable then they are much more likely to have me list the property as well as help them find the next one.