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	$184.40	6.325%	$196.0633	$196.06	$196.05	$196.10
Purchase #2	$214.70	9.278%	$234.6199	$234.62	$234.60	$234.60
Purchase #3	$109.47	8.788%	$119.0902	$119.09	$119.10	$119.10
Purchase #4	$160.84	11.852%	$179.9028	$179.90	$179.90	$179.90
Purchase #5	$236.50	4.775%	$247.7929	$247.79	$247.80	$247.80
Purchase #6	$123.77	12.796%	$139.6076	$139.61	$139.60	$139.60
Purchase #7	$219.42	8.870%	$238.8826	$238.88	$238.90	$238.90
7 purchase totals =	$1,249.10		$1,355.9593	$1,355.95	$1,355.95	$1,356.00