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	$202.96	5.385%	$213.8894	$213.89	$213.90	$213.90
Purchase #2	$121.64	4.485%	$127.0956	$127.10	$127.10	$127.10
Purchase #3	$166.83	3.105%	$172.0101	$172.01	$172.00	$172.00
Purchase #4	$143.80	11.308%	$160.0609	$160.06	$160.05	$160.10
Purchase #5	$66.72	7.178%	$71.5092	$71.51	$71.50	$71.50
Purchase #6	$10.62	5.845%	$11.2407	$11.24	$11.25	$11.20
Purchase #7	$145.60	9.216%	$159.0185	$159.02	$159.00	$159.00
7 purchase totals =	$858.17		$914.8244	$914.83	$914.80	$914.80