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	$178.40	6.529%	$190.0477	$190.05	$190.05	$190.00
Purchase #2	$142.83	7.529%	$153.5837	$153.58	$153.60	$153.60
Purchase #3	$72.31	10.763%	$80.0927	$80.09	$80.10	$80.10
Purchase #4	$20.78	10.240%	$22.9079	$22.91	$22.90	$22.90
Purchase #5	$17.66	4.284%	$18.4166	$18.42	$18.40	$18.40
Purchase #6	$157.79	6.845%	$168.5907	$168.59	$168.60	$168.60
Purchase #7	$146.47	9.105%	$159.8061	$159.81	$159.80	$159.80
7 purchase totals =	$736.24		$793.4454	$793.45	$793.45	$793.40