Flooring Tile - Ceramic Tile Up To Bath Tub?

I'm launching into tiling our small bathroom--will only need 32.5 square feet of tile. On my previous remodel I put hardibacker board down under the plastic floor covering, so I'm prepared there.

I'm reconciled to the fact that I'll have to remove the toilet and tile under it, but I was wondering about tiling right up to the edge of the cast iron/ceramic tub. I was thinking that temperature extremes might promote grout cracking later on, and that I might leave a grout line next to the tub and silicone caulk there.

Any help appreciated.

Thanks!
U

That it exactly what you are supposed to do. If the grout line is large just leave a 1/8 [approx] space and fill with color matched caulk