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	$119.56	12.628%	$134.658	$134.66	$134.65	$134.70
Purchase #2	$250.76	11.152%	$278.7248	$278.72	$278.70	$278.70
Purchase #3	$50.47	12.382%	$56.7192	$56.72	$56.70	$56.70
Purchase #4	$33.76	5.654%	$35.6688	$35.67	$35.65	$35.70
Purchase #5	$64.29	12.476%	$72.3108	$72.31	$72.30	$72.30
Purchase #6	$38.81	8.366%	$42.0568	$42.06	$42.05	$42.10
Purchase #7	$214.93	12.636%	$242.0886	$242.09	$242.10	$242.10
7 purchase totals =	$772.58		$862.2270	$862.23	$862.15	$862.30