This is a bit confusing. The way you have stated the problem is not very clear to us. Here is something I will tell you. Camera
systems such as EyeMax have the ability to link into a POS system and get a sale on camera each time and put the ticket number from the pos sale on the recorded video.
Also 16 camera systems are pretty cheap these days. Finally, if they want to be able to see more clearly, then they need different cameras. At some locations I installed 60mm lenses so my client can see the denomination of the money that is being passed across the counter. The reason for this is that sometimes people will come back in screaming and yelling "I gave your employee a 100, and they just gave me back change out of a 10..." <- that has happened at least 25 times at different store locations.
The interesting part is, we can pull it up on a giant monitor at each store right out front on the sales floor, and show the customer. To date, the customer has always been wrong. They usually feel embarassed, apologize, and then leave or, they get mad that you busted their little scam.
See we usually have the giant monitors on a conglomerate view showing whichever of 32 cameras we want, so that people know they are real, and know they are being recorded. Make sense? Theft has dropped way down. In addition to all of this, they are usually very surprised to 'hear' their voices in crystal clear clarity thanks to the super sensitive microphones installed in the systems. (you can set the pickup so high you can hear a pin drop.)
All of these systems allow remote web log in with audio.

They can also trigger multiple alarm output switches, and they are more accurate than those ultrasonic things some alarm people install.
Additionally with the right size hard drive you can easily record a years worth of data on 16 cameras in full 32 frame per second motion. You would not beleive the people we caught on these systems doing bad things, it is unreal. I recommend EyeMax, they are my favourite out of many brands. Kalatel is good too though. Some of the other brands are plain awful so read reviews of people that actually use them and do your research.