Watt Ave Tower? Or Broadway? I practically lived at both those stores when I was living in Sac and going to college at American River c. 1980.
I went on to work for Tower for several years including a 3 year stint in the mid-90s at the Sunrise location. Good times.
I was 14 in 1975 and while I was certainly familiar with The Who (my older sister had a copy of "Who's Next") I was unfamiliar with Tommy except by name and reputation. "Oldies" didn't get played on the radio much in those days as "classic rock" wasn't yet a thing.
I, of course, had no way of knowing in 1975 that there would eventually be a GH V II with Pinball Wizard on it, but even if I had I doubt I'd have waited. I was simply too big an Elton fan and HAD to have a copy of it for myself. I would even buy all his singles in those days just for the b-sides.
I've still never seen the movie but I did really like the soundtrack. It took me awhile to eventually get used to the original Who versions of all the songs. In fact, heresy as this probably is to say in front of big Who fans, but I still prefer the movie versions for most of them.