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	$210.49	5.325%	$221.6986	$221.70	$221.70	$221.70
Purchase #2	$16.72	10.574%	$18.488	$18.49	$18.50	$18.50
Purchase #3	$205.45	4.780%	$215.2705	$215.27	$215.25	$215.30
Purchase #4	$65.49	8.519%	$71.0691	$71.07	$71.05	$71.10
Purchase #5	$87.91	4.361%	$91.7438	$91.74	$91.75	$91.70
Purchase #6	$107.31	3.486%	$111.0508	$111.05	$111.05	$111.10
Purchase #7	$243.57	11.599%	$271.8217	$271.82	$271.80	$271.80
7 purchase totals =	$936.94		$1,001.1425	$1,001.14	$1,001.10	$1,001.20