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	$48.51	10.200%	$53.458	$53.46	$53.45	$53.50
Purchase #2	$49.88	5.462%	$52.6044	$52.60	$52.60	$52.60
Purchase #3	$65.32	9.824%	$71.737	$71.74	$71.75	$71.70
Purchase #4	$52.70	3.824%	$54.7152	$54.72	$54.70	$54.70
Purchase #5	$155.25	9.254%	$169.6168	$169.62	$169.60	$169.60
Purchase #6	$104.99	6.201%	$111.5004	$111.50	$111.50	$111.50
Purchase #7	$197.36	12.197%	$221.432	$221.43	$221.45	$221.40
7 purchase totals =	$674.01		$735.0638	$735.07	$735.05	$735.00