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	$205.42	5.197%	$216.0957	$216.10	$216.10	$216.10
Purchase #2	$182.64	9.864%	$200.6556	$200.66	$200.65	$200.70
Purchase #3	$114.91	4.519%	$120.1028	$120.10	$120.10	$120.10
Purchase #4	$125.44	9.534%	$137.3994	$137.40	$137.40	$137.40
Purchase #5	$157.62	6.252%	$167.4744	$167.47	$167.45	$167.50
Purchase #6	$52.99	11.680%	$59.1792	$59.18	$59.20	$59.20
Purchase #7	$191.93	6.542%	$204.4861	$204.49	$204.50	$204.50
7 purchase totals =	$1,030.95		$1,105.3932	$1,105.40	$1,105.40	$1,105.50