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	$21.94	5.360%	$23.116	$23.12	$23.10	$23.10
Purchase #2	$148.43	8.123%	$160.487	$160.49	$160.50	$160.50
Purchase #3	$105.81	3.485%	$109.4975	$109.50	$109.50	$109.50
Purchase #4	$214.43	3.401%	$221.7228	$221.72	$221.70	$221.70
Purchase #5	$85.27	7.381%	$91.5638	$91.56	$91.55	$91.60
Purchase #6	$48.60	7.533%	$52.261	$52.26	$52.25	$52.30
Purchase #7	$58.35	6.164%	$61.9467	$61.95	$61.95	$61.90
7 purchase totals =	$682.83		$720.5948	$720.60	$720.55	$720.60