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	$62.52	5.180%	$65.7585	$65.76	$65.75	$65.80
Purchase #2	$107.71	3.823%	$111.8278	$111.83	$111.85	$111.80
Purchase #3	$206.68	5.293%	$217.6196	$217.62	$217.60	$217.60
Purchase #4	$84.53	7.568%	$90.9272	$90.93	$90.95	$90.90
Purchase #5	$183.92	5.284%	$193.6383	$193.64	$193.65	$193.60
Purchase #6	$196.96	13.294%	$223.1439	$223.14	$223.15	$223.10
Purchase #7	$42.42	10.589%	$46.9119	$46.91	$46.90	$46.90
7 purchase totals =	$884.74		$949.8272	$949.83	$949.85	$949.70