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	$101.50	8.832%	$110.4645	$110.46	$110.45	$110.50
Purchase #2	$205.76	7.432%	$221.0521	$221.05	$221.05	$221.10
Purchase #3	$119.73	5.670%	$126.5187	$126.52	$126.50	$126.50
Purchase #4	$110.61	5.260%	$116.4281	$116.43	$116.45	$116.40
Purchase #5	$238.29	8.461%	$258.4517	$258.45	$258.45	$258.50
Purchase #6	$71.84	8.738%	$78.1174	$78.12	$78.10	$78.10
Purchase #7	$110.72	10.650%	$122.5117	$122.51	$122.50	$122.50
7 purchase totals =	$958.45		$1,033.5442	$1,033.54	$1,033.50	$1,033.60