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	$95.42	13.325%	$108.1347	$108.13	$108.15	$108.10
Purchase #2	$120.38	4.749%	$126.0968	$126.10	$126.10	$126.10
Purchase #3	$142.56	12.235%	$160.0022	$160.00	$160.00	$160.00
Purchase #4	$95.46	5.572%	$100.779	$100.78	$100.80	$100.80
Purchase #5	$180.39	5.576%	$190.4485	$190.45	$190.45	$190.40
Purchase #6	$10.57	5.745%	$11.1772	$11.18	$11.20	$11.20
Purchase #7	$101.42	9.258%	$110.8095	$110.81	$110.80	$110.80
7 purchase totals =	$746.20		$807.4479	$807.45	$807.50	$807.40