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	$214.84	3.611%	$222.5979	$222.60	$222.60	$222.60
Purchase #2	$102.43	4.289%	$106.8232	$106.82	$106.80	$106.80
Purchase #3	$140.66	7.715%	$151.5119	$151.51	$151.50	$151.50
Purchase #4	$161.56	7.137%	$173.0905	$173.09	$173.10	$173.10
Purchase #5	$11.50	4.529%	$12.0208	$12.02	$12.00	$12.00
Purchase #6	$243.30	13.458%	$276.0433	$276.04	$276.05	$276.00
Purchase #7	$106.27	5.823%	$112.4581	$112.46	$112.45	$112.50
7 purchase totals =	$980.56		$1,054.5457	$1,054.54	$1,054.50	$1,054.50