If you have 5 different websites (e.g product items, like separate web site for toys, camera, phones etc.) hosting on to the same hosting account, does it matter in SERPs or how Google looks at it?
If you have links from one site to other, then those links will not worth much. Other then this, there is no problem hosting sites on same IP.
Have at look at http://forums.digitalpoint.com/showthread.php?p=6818967#post6818967. It discusses whether or not all links are seen as valuable, even those within the same site or on the same IP address.