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	$160.95	6.625%	$171.6129	$171.61	$171.60	$171.60
Purchase #2	$189.87	8.336%	$205.6976	$205.70	$205.70	$205.70
Purchase #3	$54.62	10.367%	$60.2825	$60.28	$60.30	$60.30
Purchase #4	$100.99	10.402%	$111.495	$111.50	$111.50	$111.50
Purchase #5	$28.70	13.119%	$32.4652	$32.47	$32.45	$32.50
Purchase #6	$87.74	3.557%	$90.8609	$90.86	$90.85	$90.90
Purchase #7	$134.91	13.745%	$153.4534	$153.45	$153.45	$153.50
7 purchase totals =	$757.78		$825.8675	$825.87	$825.85	$826.00