deviceanywhere.com and perfectomobile.com offer the ability to test on real devices, but prices are completely ridiculous for normal people (IMHO, but check them out yourself).
However, Device Anywhere offers a free service on a small number of half-decent devices, and I think iOS 5 on an iPhone is available (might even be iOS 6).
Good thing is, iOS, unlike any other mobile OS, behaves very similar on its two most recent OS's. The others all have major differences (ICS v Jelly Bean, Win Phone 7/8, BB etc.).
That being said, if you are half serious or more about your site then you need to test on real devices (or a real-device simulator). Trust me, you will be in for one hell of a surprise when you do - especially if you use jQuery (or any other non-basic JS).