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	$87.81	4.709%	$91.945	$91.95	$91.95	$91.90
Purchase #2	$105.43	5.444%	$111.1696	$111.17	$111.15	$111.20
Purchase #3	$9.46	8.339%	$10.2489	$10.25	$10.25	$10.20
Purchase #4	$161.37	11.430%	$179.8146	$179.81	$179.80	$179.80
Purchase #5	$103.64	10.315%	$114.3305	$114.33	$114.35	$114.30
Purchase #6	$110.70	4.703%	$115.9062	$115.91	$115.90	$115.90
Purchase #7	$87.67	13.495%	$99.5011	$99.50	$99.50	$99.50
7 purchase totals =	$666.08		$722.9159	$722.92	$722.90	$722.80