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	$221.39	10.721%	$245.1252	$245.13	$245.15	$245.10
Purchase #2	$203.49	12.490%	$228.9059	$228.91	$228.90	$228.90
Purchase #3	$99.70	11.399%	$111.0648	$111.06	$111.05	$111.10
Purchase #4	$16.95	7.348%	$18.1955	$18.20	$18.20	$18.20
Purchase #5	$138.35	7.618%	$148.8895	$148.89	$148.90	$148.90
Purchase #6	$115.74	6.849%	$123.667	$123.67	$123.65	$123.70
Purchase #7	$71.46	11.447%	$79.64	$79.64	$79.65	$79.60
7 purchase totals =	$867.08		$955.4879	$955.50	$955.50	$955.50