You could create the query using a sprintf call that prints the number of digits you expect, i.e.

$fv = sprintf("%1.2f", $dv);
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where $fv is the value to put in the query and $dv is the value from the database.

What that really does is use decimal representation and string conversion to set the accuracy of the floating point value. It's equivalent to querying the database for matches to a given level of accuracy:

SELECT * FROM table WHERE abs(float - 0.98) < 0.001;
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For some reason, the comparison version bothers a lot of programmers, where chopping off digits in a string representation doesn't.