Auto rounding not correct with tax-included calculations

I hope the title makes sense. So for some online orders, one can add a tip. The tip includes tax and the calculation is configured as such.

What I’m experiencing is that the auto round +/- to nearest 0.05 applies on the pre-tax total and if there is a tip that does not end in 0 or 5 then the ticket total is off by a cent or two here and there. “Use plain sum” doesn’t seem to change the behaviour.

Any thoughts? TIA

example ticket - expected total should be 53.55 with Round+ calculation of .02

calculation selector: