question about count system and index# use

Should the true count be rounded off, how should it be used with the indexes?
Examples:

True count says stand 15 vs 10 at tc +6 or more. say the tc is +5.8 should this be rounded up to 6 and stand on the hand?

True count needs to be -1 or less to hit 12 vs 4, what if the tc is
-.9 should this be rounded up to -1 and stand or should the hand be hit?

Thanks.