well a 275 on the back are goign to be FAR to narrow for a 10.5 inch rim it will look VERY VERY bad, picture a civic with stretched out skinny little tires. It may even be unsafe... think about it this way. A 275/40/17 on a 10.5 inch rim is the same as running a 205-215mm wide tire on an 8 inch wide rim or worse.
So you have some choices
1) Sell the rear rims and get 17 by 8s out back and run a 245 tire, this will allow you to rotate with out worry.
2) Sell the rear rims and buy a 17 by 9 rims out back and run a 275/40/17 (THE correct rim/tire size) but the difference is not huge.
3) Run the correct size tire for the 17 by 10.5 inch rims which is a 305-315. If you cant afford it then sell the rims... dont run wide rims if your not going to use em. They are expensive... but thats the price you pay I guess...
If you dont rotate the front tires get ready for some horrendus road noise ahead
keeping them aligned and inspected every 6k and 3k respectivly definatly will help though, tire pressure is also key to tire wear.