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	$191.42	8.690%	$208.0544	$208.05	$208.05	$208.10
Purchase #2	$106.50	4.706%	$111.5119	$111.51	$111.50	$111.50
Purchase #3	$154.36	3.591%	$159.9031	$159.90	$159.90	$159.90
Purchase #4	$44.59	3.832%	$46.2987	$46.30	$46.30	$46.30
Purchase #5	$119.77	8.138%	$129.5169	$129.52	$129.50	$129.50
Purchase #6	$50.88	12.202%	$57.0884	$57.09	$57.10	$57.10
Purchase #7	$142.31	6.555%	$151.6384	$151.64	$151.65	$151.60
7 purchase totals =	$809.83		$864.0118	$864.01	$864.00	$864.00