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	$205.26	8.238%	$222.1693	$222.17	$222.15	$222.20
Purchase #2	$47.67	10.337%	$52.5976	$52.60	$52.60	$52.60
Purchase #3	$179.34	6.831%	$191.5907	$191.59	$191.60	$191.60
Purchase #4	$240.98	13.688%	$273.9653	$273.97	$273.95	$274.00
Purchase #5	$107.70	3.148%	$111.0904	$111.09	$111.10	$111.10
Purchase #6	$19.81	13.206%	$22.4261	$22.43	$22.45	$22.40
Purchase #7	$48.92	6.682%	$52.1888	$52.19	$52.20	$52.20
7 purchase totals =	$849.68		$926.0282	$926.04	$926.05	$926.10