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	$167.91	5.302%	$176.8126	$176.81	$176.80	$176.80
Purchase #2	$82.37	8.680%	$89.5197	$89.52	$89.50	$89.50
Purchase #3	$122.92	4.490%	$128.4391	$128.44	$128.45	$128.40
Purchase #4	$179.94	13.768%	$204.7141	$204.71	$204.70	$204.70
Purchase #5	$138.66	3.386%	$143.355	$143.36	$143.35	$143.40
Purchase #6	$185.75	3.447%	$192.1528	$192.15	$192.15	$192.20
Purchase #7	$101.65	10.103%	$111.9197	$111.92	$111.90	$111.90
7 purchase totals =	$979.20		$1,046.9130	$1,046.91	$1,046.85	$1,046.90