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	$66.49	8.860%	$72.381	$72.38	$72.40	$72.40
Purchase #2	$141.33	12.509%	$159.009	$159.01	$159.00	$159.00
Purchase #3	$173.58	12.779%	$195.7618	$195.76	$195.75	$195.80
Purchase #4	$213.70	4.727%	$223.8016	$223.80	$223.80	$223.80
Purchase #5	$95.31	8.265%	$103.1874	$103.19	$103.20	$103.20
Purchase #6	$32.53	9.370%	$35.5781	$35.58	$35.60	$35.60
Purchase #7	$187.88	6.828%	$200.7084	$200.71	$200.70	$200.70
7 purchase totals =	$910.82		$990.4273	$990.43	$990.45	$990.50