Your ceilings are low enough, I would tile all the way up.

Couple things to consider. First, how flat are your ceilings? Second, how would the layout look to the ceiling?

I went to the ceiling in my kids bath. One of the things I ran into was an out of level ceiling. The whole room was plaster that got ripped out. If you've ever had the pleasure of re-sheetrocking 50 year old framing you quickly figure out that plumb and square might as well have been Mandarin Chinese words to the framers. Although extremely sturdy, the framers knew the flaws would be hidden by the plaster. Sheetrock exposes all those flaws. What it amounts to is extra installation time as each cut is specific to each spot. You can't just lop off 2" from every tile, cut 20 of them, then go back to installing. If you take your time, and plan carefully this is easily handled.

Along that same line, is planning well beforehand your layout. I'd prefer a full tile at the tub line, but only if it doesn't leave a sliver of tile at the ceiling. If you have a sliver, you'd be better to make equal cuts at the bottom and top courses so things look balanced. You can also "fudge" the grout lines slightly if need be.

I would take accurate measurements at several locations around the tub, up to the ceiling and do a dry fitting. Put some tape down on the floor to represent the wall space, then layout your tiles with the spacer you chosen. You'll immediately see how everything will fit. Ultimately, if it looks ugly leave the tile short of the ceiling.

With a ceiling that low, I'd tile it all the way up. It's not that much more in materials, and it'll save you money in repairs down the line.

Sometimes you can actually save money because you don't have to buy as many expensive bullnose tiles.