I find it a bit specific how you want to look at market change specifically for every 15 minutes. After a bit of research though, I found this pretty good website (https://www.kitco.com/bitcoin-price-charts-usd/) where you can see real market changes starting from every 1, 3, 5, 15 min and up to 45 min.

SO this might be the one you're looking after. Also this site goes beyond the minute intervals and stretches into the more familiar timings like hourly, weekly, monthly and even yearly, though all these have specific timings just like the minutes intervals described earlier.