Hey!
I have worked on a very similar application once in my graduation thesis, we needed to plot some star brightnesses from data uploaded by some amateur astronomers, and we did a little plot to show what they just uploaded, its a bit different from sales data! But the same concepts apply in the programming of the website!
I have been the lead front-end developer for a small brazilian educational games studio, and have worked on multiple websites and applications, using C, C++,. C#, Python, JavaScript, CSS and HTML5, the website I mentioned was developed in Django, and I have lots of experience with it and Plotly, Matplotlib.
I also have experience working with databases and configuring them, I have previously worked with MySQL and PostgreSQL
I believe I can help you with your project!
Thank you for the consideration!