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	$101.32	6.756%	$108.1652	$108.17	$108.15	$108.20
Purchase #2	$15.65	6.701%	$16.6987	$16.70	$16.70	$16.70
Purchase #3	$77.87	9.700%	$85.4234	$85.42	$85.40	$85.40
Purchase #4	$143.73	5.371%	$151.4497	$151.45	$151.45	$151.40
Purchase #5	$108.32	3.335%	$111.9325	$111.93	$111.95	$111.90
Purchase #6	$145.56	3.579%	$150.7696	$150.77	$150.75	$150.80
Purchase #7	$11.78	12.137%	$13.2097	$13.21	$13.20	$13.20
7 purchase totals =	$604.23		$637.6488	$637.65	$637.60	$637.60