Are we supposed to round up or down our dollar amounts. For example, if my W-2 form indicates $152.49, do I enter $152 or $153?

Enter $152. Round .50 up to $1.00 and .49 down. 

Yes, If rounding is used, it must be used consistently. Withheld tax amounts should be rounded to the nearest whole dollar by dropping amounts under 50 cents and increasing amounts from 50 to 99 cents to the next dollar. For example, $2.30 becomes $2 and $2.50 becomes $3.