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	$235.60	7.621%	$253.5551	$253.56	$253.55	$253.60
Purchase #2	$111.32	11.353%	$123.9582	$123.96	$123.95	$124.00
Purchase #3	$160.49	12.447%	$180.4662	$180.47	$180.45	$180.50
Purchase #4	$243.51	4.156%	$253.6303	$253.63	$253.65	$253.60
Purchase #5	$78.76	6.117%	$83.5777	$83.58	$83.60	$83.60
Purchase #6	$65.72	8.335%	$71.1978	$71.20	$71.20	$71.20
Purchase #7	$16.30	7.278%	$17.4863	$17.49	$17.50	$17.50
7 purchase totals =	$911.70		$983.8716	$983.89	$983.90	$984.00