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	$207.95	12.820%	$234.6092	$234.61	$234.60	$234.60
Purchase #2	$11.43	5.688%	$12.0801	$12.08	$12.10	$12.10
Purchase #3	$189.92	3.284%	$196.157	$196.16	$196.15	$196.20
Purchase #4	$238.86	11.643%	$266.6705	$266.67	$266.65	$266.70
Purchase #5	$229.61	11.634%	$256.3228	$256.32	$256.30	$256.30
Purchase #6	$38.78	12.315%	$43.5558	$43.56	$43.55	$43.60
Purchase #7	$117.33	8.124%	$126.8619	$126.86	$126.85	$126.90
7 purchase totals =	$1,033.88		$1,136.2573	$1,136.26	$1,136.20	$1,136.40