Me again with more parking malarkey...

I think I've spent a bit too much time on the same task and numbers/formulas have started to all roll into one ball of pure annoyance. Thus, I'm back.

I have a list of parking transactions with the amount paid, however, these don't always match the tariffs (if people don't have correct change etc.). I've made a table showing available payments per tariff and have been using a combination of INDEX/MATCH/MIN to try and get it to lookup the available values and round it down. I've attached a photo sort of showing this...

https://imgur.com/a/gDjnU8m

Essentially, I need to convert the Amount field into the cost field using the table shown. So in this example, It's Tariff 7, and they've paid £4.15. Using the table this needs to display £3.90, it will always be the lower value so always rounded down. I've gone through plenty of permutations and feel as if I'm missing something really rudimentary. I'm sure walking away and coming back to it is the way but on a schedule so here I am.

As always, any help much appreciated.