I was at a local Irving Mainway store last August, and beginning on August 25, that particular Irving location no longer accepts any $100 bills - not even the latest issue. It's possible that all Irving Mainway locations in my hometown may be universal with that policy now - seeing all the horrific news of armed robberies in recent years.
Wait a minute... Stores are still refusing even newer $100s? Are stores that gullible to believe a $100 bill of the 2004 issue can be counterfeited easily despite the security features?
Then again, they probably no longer accept them due to security reasons - not just counterfeiting, but in an effort to combat possible robberies. Besides, $100 bills are mainly used for rent payments, car loan payments, payments on big-ticket items, etc. People nowadays pay for groceries with plastic debit cards most of the time, or they rely on $20s. They are usually uncertain how much money they may spend on groceries (they may spend $40, they may spend $60, etc.), so they just go to the nearest ATM and take out the cash in $20s. Most supermarkets do have onsite ATMs (my neighbourhood supermarket does have a Scotiabank ATM onsite, btw).
To sum it up: merchants don't want to take any risks, so they still treat $100 bills with a grain of salt regardless if they are current or new issue, and regardless of any circumstance.