Circular saw with a standard blade will easily slice through plastic. Sawzall or oscillating saw will work great too. Tin snips or shears will work as well.
Just cut mine with Sawzall and metal blade. Not straight cuts, but not too worried about that. Going through some ideas to raise them up on the 275-gallon totes so I can load and unload totes without the need to remove them. Only have 8 from my 4 330-gallon totes to play with.
Some members have multiple IBC totes with the plastic roofs and it does look like a gnome village. T.Jeff Veal comes to mind.
I’ve never cut one. Put the blade backwards in a skilsaw would be a good option. Cuts vinyl siding nice. A masonry blade would work too.