As far as Mcafee home is concerned you can not stop the real time scanner scanning every file you open or copy. You can only exclude files and folders in custom and scheduled scans.
The Enterprise version is the 1 that has exclusions for normal scans.
Mcafee has a trusted list area items are put in tere if Mcafee detects a virus and asks you if you want to trust it. Really never seen that happen try a scan and see if you are asked to trust the file.
Managing quarantined and trusted items
When McAfee detects a potential security threat, you are prompted to deal with it appropriately. When McAfee quarantines threats, it encrypts and isolates them in a folder to prevent the files or programs from harming your PC. McAfee keeps a list of your quarantined and trusted items. View the list for details, then choose to permanently delete items, send items to McAfee for analysis, and restore items that you trust and know are safe.
Actually I think trusting is only for PUPS as mantioned below
Review potentially unwanted programs
When McAfee detects potentially unwanted programs during a scan, it asks you to review the results and decide which programs should be quarantined, and which should be trusted.
In the list of potentially unwanted programs, you can open details on each item to see the name of the file, its location on your PC, and the threats it contains.
You can quarantine all potentially unwanted programs at once if you know that the items on the list are unwanted, or you can quarantine programs individually. If you recognize all of the programs as safe, you can trust them all together. When McAfee quarantines items, it encrypts and isolates them in a folder to prevent the files or programs from harming your PC.