About Steam Community Market

When you put cards on market you confirm this on your steam app ? and your cards is in sell list not waiting mobile confirmation?
I remember once i put few cards and confirm from steam app ,but later i see that they are not in sell list :D So i cancel all and do it again and all worked ,if this is not a case ,contact steam support ,they will help you :)

Pretty sure it is a currency conversion issue as Mullins said. Americans I know never have issues, but as a Canadian, sometimes I will because of how currency gets rounded to USD I guess. I know it's not a case of people just deciding to buy more expensive items because I screwed up once when placing an order, setting my buying price to much higher then the cheapest listing for an item (decimal input didn't register, I was tired and didn't realize), the order was also to purchase 20 of the item. It instantly purchased the 20 cheapest listings for the item.

That's where Steam tax jumps up 0.01 so you would still get the same after tax, so they just use the lower number.

Ah, that last part is the important one.
That is strange and should not be how Steam market works for cards. Those are always sold on the "lowest price to highest" basis. So if you put a card up for 20, and someone says they want to buy for 25, they pay you that 20 and your card gets bought (assuming there are no cards sold cheaper).
Can you link the market page of the card in question?