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	$191.69	3.533%	$198.4624	$198.46	$198.45	$198.50
Purchase #2	$144.64	6.263%	$153.6988	$153.70	$153.70	$153.70
Purchase #3	$225.81	6.436%	$240.3431	$240.34	$240.35	$240.30
Purchase #4	$112.40	4.780%	$117.7727	$117.77	$117.75	$117.80
Purchase #5	$134.87	4.235%	$140.5817	$140.58	$140.60	$140.60
Purchase #6	$154.89	3.551%	$160.3901	$160.39	$160.40	$160.40
Purchase #7	$50.71	9.487%	$55.5209	$55.52	$55.50	$55.50
7 purchase totals =	$1,015.01		$1,066.7697	$1,066.76	$1,066.75	$1,066.80