Snow Tire Size

I am not a tire specialist but from past readings on tires, I think the 205/70R15 is too large. The tire height of 195/65 rides 126.75mm vs 143.50mm on the 205/70. The difference is 16.75mm. In general, you don't go oversize it by more than 10% of the original (which is 12.67mm). But then again, this is what I recall from past readings only and I may be wrong. For myself,I wouldn't use it.

 

Some sites say 3%.
195-65R15 vs 205-70R15 - Tire and Wheel Plus Sizing | Tire Size Calculator

If you want to save money mount the snow tires to see how much clearance you have. And turn the wheel all the way (lft & rt) to make sure no interference.

 

If you look at the information from Tirerack below regarding oversizing guides, +5 to 10% is the general rule. When you exceed that allowance, it will affect your speed odemeter readings and also the braking performance. Even if the larger tires do not scratch the wheel wells when you mounted them on, it doesn't mean that it is safe. When you go over bumps, the shock absorbers will be compressed and hence the top of the tires may come to contact with the top of the wheel wells.

Tire Tech Information - Plus Size Wheels & Tires
(See the very bottom.)

 

This question comes up often, and yeah, used oversized tires, 'cause they're on hand, isn't a good idea. Here's a Corolla rim that'll work with snows on a 3rd Prius, very likely with yours too:

Corolla steel rim, part no: 42611-02471 (2003-2008 corolla or matrix, CE, LS, S)
steel rim lug nuts, part no: 90942-01007 (plain, open-ended, galvanized)