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	$193.50	6.729%	$206.5206	$206.52	$206.50	$206.50
Purchase #2	$61.78	9.538%	$67.6726	$67.67	$67.65	$67.70
Purchase #3	$183.91	8.619%	$199.7612	$199.76	$199.75	$199.80
Purchase #4	$140.71	3.362%	$145.4407	$145.44	$145.45	$145.40
Purchase #5	$219.65	3.129%	$226.5228	$226.52	$226.50	$226.50
Purchase #6	$111.76	5.422%	$117.8196	$117.82	$117.80	$117.80
Purchase #7	$102.43	9.160%	$111.8126	$111.81	$111.80	$111.80
7 purchase totals =	$1,013.74		$1,075.5501	$1,075.54	$1,075.45	$1,075.50