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	$91.72	6.688%	$97.8542	$97.85	$97.85	$97.90
Purchase #2	$111.51	3.519%	$115.434	$115.43	$115.45	$115.40
Purchase #3	$173.98	11.363%	$193.7493	$193.75	$193.75	$193.70
Purchase #4	$139.40	11.283%	$155.1285	$155.13	$155.15	$155.10
Purchase #5	$248.72	13.152%	$281.4317	$281.43	$281.45	$281.40
Purchase #6	$29.79	13.522%	$33.8182	$33.82	$33.80	$33.80
Purchase #7	$213.75	4.568%	$223.5141	$223.51	$223.50	$223.50
7 purchase totals =	$1,008.87		$1,100.9300	$1,100.92	$1,100.95	$1,100.80