So, the "Label" field contains a string and the last value is a decimal number (stored as string). In that case to label the values ending on 0 or 5, you could still use the same sample, however, it is necessary to convert the string to a number using the Number function:
if (Number(label) % 5 == 0) {
return $feature["GEOMETRIA_"] + "-" + $feature["label"] + "m";
} else {
return "";
}
In case only the last value is a decimal stored as a string (what decimal sign are you using, a dot or a comma?), you could detect that and include that as an additional condition in the expression. To be able to know how to the data is stored, could you include a screenshot of your attribute table showing the values of the Label field?