Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$209.30	13.621%	$237.8088	$237.81	$237.80	$237.80
Purchase #2	$225.44	3.556%	$233.4566	$233.46	$233.45	$233.50
Purchase #3	$138.44	8.295%	$149.9236	$149.92	$149.90	$149.90
Purchase #4	$143.61	11.613%	$160.2874	$160.29	$160.30	$160.30
Purchase #5	$174.38	4.619%	$182.4346	$182.43	$182.45	$182.40
Purchase #6	$68.60	4.813%	$71.9017	$71.90	$71.90	$71.90
Purchase #7	$56.46	13.601%	$64.1391	$64.14	$64.15	$64.10
7 purchase totals =	$1,016.23		$1,099.9518	$1,099.95	$1,099.95	$1,099.90