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	$243.52	7.831%	$262.5901	$262.59	$262.60	$262.60
Purchase #2	$130.43	8.549%	$141.5805	$141.58	$141.60	$141.60
Purchase #3	$151.90	13.707%	$172.7209	$172.72	$172.70	$172.70
Purchase #4	$70.68	13.490%	$80.2147	$80.21	$80.20	$80.20
Purchase #5	$30.26	4.218%	$31.5364	$31.54	$31.55	$31.50
Purchase #6	$231.45	6.742%	$247.0544	$247.05	$247.05	$247.10
Purchase #7	$102.91	10.368%	$113.5797	$113.58	$113.60	$113.60
7 purchase totals =	$961.15		$1,049.2767	$1,049.27	$1,049.30	$1,049.30