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	$186.57	5.135%	$196.1504	$196.15	$196.15	$196.20
Purchase #2	$146.47	3.229%	$151.1995	$151.20	$151.20	$151.20
Purchase #3	$242.66	13.714%	$275.9384	$275.94	$275.95	$275.90
Purchase #4	$170.41	3.397%	$176.1988	$176.20	$176.20	$176.20
Purchase #5	$122.77	6.378%	$130.6003	$130.60	$130.60	$130.60
Purchase #6	$103.56	11.178%	$115.1359	$115.14	$115.15	$115.10
Purchase #7	$17.45	4.597%	$18.2522	$18.25	$18.25	$18.30
7 purchase totals =	$989.89		$1,063.4755	$1,063.48	$1,063.50	$1,063.50