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	$108.60	5.612%	$114.6946	$114.69	$114.70	$114.70
Purchase #2	$227.69	10.450%	$251.4836	$251.48	$251.50	$251.50
Purchase #3	$160.52	3.218%	$165.6855	$165.69	$165.70	$165.70
Purchase #4	$61.55	7.227%	$65.9982	$66.00	$66.00	$66.00
Purchase #5	$17.62	4.857%	$18.4758	$18.48	$18.50	$18.50
Purchase #6	$172.40	13.809%	$196.2067	$196.21	$196.20	$196.20
Purchase #7	$145.65	4.672%	$152.4548	$152.45	$152.45	$152.50
7 purchase totals =	$894.03		$964.9992	$965.00	$965.05	$965.10