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	$95.98	3.648%	$99.4814	$99.48	$99.50	$99.50
Purchase #2	$13.96	5.273%	$14.6961	$14.70	$14.70	$14.70
Purchase #3	$110.68	11.598%	$123.5167	$123.52	$123.50	$123.50
Purchase #4	$69.54	7.160%	$74.5191	$74.52	$74.50	$74.50
Purchase #5	$9.50	6.201%	$10.0891	$10.09	$10.10	$10.10
Purchase #6	$112.53	5.261%	$118.4502	$118.45	$118.45	$118.50
Purchase #7	$141.60	4.156%	$147.4849	$147.48	$147.50	$147.50
7 purchase totals =	$553.79		$588.2375	$588.24	$588.25	$588.30