You cannot, and you will never be able to open your Canon raw files directly in CS5.
That camera was supported for the first time in ACR 8.3, which requires at least Photoshop CC to run.
You either subscribe to Photoshop CC (Creative Cloud) on a monthly basis, or you use the free stand alone to convert every batch of Canon raw files from that camera model to convert them to raw DNGs that you can then open in CS5.
Photoshop CS6 will run ACR 8.7.
Use the DNG converter: Adobe - Adobe Camera Raw and DNG Converter : For Windows : Adobe DNG Converter 8.7
Benjamin, you are correct, of course. I'm running ACR 8.7.1 on SCS6 13.0.6 myself.
The OP is in CS5, and, in senior moment, I overlooked the possibility of upgrading from CS5 to CS6 for $199, unless that offer has expired. There was something that expires today, Dec 22, but I can't remember what.