Do you mean "casino"?
There isn't a checkbox for poker, so I'm not exactly sure what you're trying to do.
ROMLister is merely a search engine, so if there is a keyword in the xml data that is common among the games you want to avoid, all we need to do is locate that keyword and add it to the exclude list.
For example, the game "poker ladies" is tagged from catver as being in the "<category>Casino *Mature*</category>"
category. By unchecking "casino" in the romlister GUI, that game never made it into my list.
However, the game "pairs", which appears to be a card game, is under the "<category>Puzzle / Cards *Mature*</category>" Ok, that's a card game, but apparently not a casino game, according to catver.
If you look at the -find text in the main GUI, you'll see at the very end when I checked off the "casino" option, it added the following text: "& !('BIOS' | casino)"
Since there is no direct checkbox for "cards" you can go into that -find text and dig them out yourself. Change the text from:
& !('BIOS' | casino)
to
& !('BIOS' | casino | cards)
and all the card games will go away. This is under the advanced searches tutorial on the wiki.
For any game that made it into your final list that you really didn't want, 2x click the name when romlister is showing you your working list, and it will display the XML data for that game. You should be able to see the category data pretty much at the top. You can add whatever you want to the find list and start again. Just note that each time you hit the GO! button, it will *add* roms into your working list, so if you're still finding things to filter on, make sure you close the working list box before running the next search.