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	$225.84	13.711%	$256.8049	$256.80	$256.80	$256.80
Purchase #2	$89.32	3.810%	$92.7231	$92.72	$92.70	$92.70
Purchase #3	$128.77	8.850%	$140.1661	$140.17	$140.15	$140.20
Purchase #4	$65.59	8.325%	$71.0504	$71.05	$71.05	$71.10
Purchase #5	$62.27	3.516%	$64.4594	$64.46	$64.45	$64.50
Purchase #6	$221.83	5.758%	$234.603	$234.60	$234.60	$234.60
Purchase #7	$221.61	7.170%	$237.4994	$237.50	$237.50	$237.50
7 purchase totals =	$1,015.23		$1,097.3063	$1,097.30	$1,097.25	$1,097.40