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	$173.84	6.688%	$185.4664	$185.47	$185.45	$185.50
Purchase #2	$11.50	5.689%	$12.1542	$12.15	$12.15	$12.20
Purchase #3	$185.54	4.748%	$194.3494	$194.35	$194.35	$194.30
Purchase #4	$239.71	12.382%	$269.3909	$269.39	$269.40	$269.40
Purchase #5	$127.61	9.630%	$139.8988	$139.90	$139.90	$139.90
Purchase #6	$25.98	11.186%	$28.8861	$28.89	$28.90	$28.90
Purchase #7	$111.63	11.619%	$124.6003	$124.60	$124.60	$124.60
7 purchase totals =	$875.81		$954.7461	$954.75	$954.75	$954.80