That is not annoying at all. Almost everything sells eventually, especially at a point-99. As a matter of fact, I rarely set above the 12-hour time period because things sell so fast. You simply spend more.

I read somewhere that, in real life, 599.99 fools nobody. We all know instinctively that its just about the same as 600. When I sell things I try and use numbers such as 587.76 - the brain doesn't automatically equate that with 600 (or whatever number you could round it to), especially if you use a few prime numbers in your price.

Of course this could all be pop-science pseudo-psychology crap, but it seems to work well for me :)

I once sold something (can't remember what) for 345g67s89c the guy that bought it sent me a letter saying part of why he bought it was because he thought my price was funny.

I will almost never undercut by more than a few silver, and it doesn't bother me at all if someone chooses to buy my competitor's item for 6g over my 5.99g, that's fine. I can assure you that there are plenty of buyers who will simply buy the lowest priced item. I also don't see why anyone would look down on someone who undercuts by a silver?