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	$165.49	6.767%	$176.6887	$176.69	$176.70	$176.70
Purchase #2	$243.60	12.410%	$273.8308	$273.83	$273.85	$273.80
Purchase #3	$217.32	9.240%	$237.4004	$237.40	$237.40	$237.40
Purchase #4	$81.65	9.719%	$89.5856	$89.59	$89.60	$89.60
Purchase #5	$191.70	4.596%	$200.5105	$200.51	$200.50	$200.50
Purchase #6	$55.43	10.287%	$61.1321	$61.13	$61.15	$61.10
Purchase #7	$9.89	4.118%	$10.2973	$10.30	$10.30	$10.30
7 purchase totals =	$965.08		$1,049.4454	$1,049.45	$1,049.50	$1,049.40