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	$101.86	4.722%	$106.6698	$106.67	$106.65	$106.70
Purchase #2	$168.50	7.325%	$180.8426	$180.84	$180.85	$180.80
Purchase #3	$118.56	10.667%	$131.2068	$131.21	$131.20	$131.20
Purchase #4	$54.83	3.454%	$56.7238	$56.72	$56.70	$56.70
Purchase #5	$166.78	11.311%	$185.6445	$185.64	$185.65	$185.60
Purchase #6	$30.63	12.316%	$34.4024	$34.40	$34.40	$34.40
Purchase #7	$42.50	13.107%	$48.0705	$48.07	$48.05	$48.10
7 purchase totals =	$683.66		$743.5604	$743.55	$743.50	$743.50