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	$94.71	11.197%	$105.3147	$105.31	$105.30	$105.30
Purchase #2	$111.27	6.113%	$118.0719	$118.07	$118.05	$118.10
Purchase #3	$156.93	13.434%	$178.012	$178.01	$178.00	$178.00
Purchase #4	$134.39	10.446%	$148.4284	$148.43	$148.45	$148.40
Purchase #5	$247.79	11.240%	$275.6416	$275.64	$275.65	$275.60
Purchase #6	$131.31	9.248%	$143.4535	$143.45	$143.45	$143.50
Purchase #7	$100.53	11.172%	$111.7612	$111.76	$111.75	$111.80
7 purchase totals =	$976.93		$1,080.6833	$1,080.67	$1,080.65	$1,080.70