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	$193.78	8.798%	$210.8288	$210.83	$210.85	$210.80
Purchase #2	$100.32	11.335%	$111.6913	$111.69	$111.70	$111.70
Purchase #3	$48.32	7.814%	$52.0957	$52.10	$52.10	$52.10
Purchase #4	$197.26	13.335%	$223.5646	$223.56	$223.55	$223.60
Purchase #5	$85.45	13.645%	$97.1097	$97.11	$97.10	$97.10
Purchase #6	$88.61	11.810%	$99.0748	$99.07	$99.05	$99.10
Purchase #7	$13.35	3.148%	$13.7703	$13.77	$13.75	$13.80
7 purchase totals =	$727.09		$808.1352	$808.13	$808.10	$808.20