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	$151.92	10.569%	$167.9764	$167.98	$168.00	$168.00
Purchase #2	$61.47	3.505%	$63.6245	$63.62	$63.60	$63.60
Purchase #3	$89.54	11.783%	$100.0905	$100.09	$100.10	$100.10
Purchase #4	$200.37	10.118%	$220.6434	$220.64	$220.65	$220.60
Purchase #5	$146.84	5.139%	$154.3861	$154.39	$154.40	$154.40
Purchase #6	$122.71	4.266%	$127.9448	$127.94	$127.95	$127.90
Purchase #7	$61.58	13.773%	$70.0614	$70.06	$70.05	$70.10
7 purchase totals =	$834.43		$904.7271	$904.72	$904.75	$904.70