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	$100.98	5.782%	$106.8187	$106.82	$106.80	$106.80
Purchase #2	$206.59	11.567%	$230.4863	$230.49	$230.50	$230.50
Purchase #3	$23.34	5.436%	$24.6088	$24.61	$24.60	$24.60
Purchase #4	$237.99	7.775%	$256.4937	$256.49	$256.50	$256.50
Purchase #5	$233.29	4.103%	$242.8619	$242.86	$242.85	$242.90
Purchase #6	$143.62	10.552%	$158.7748	$158.77	$158.75	$158.80
Purchase #7	$216.69	7.759%	$233.503	$233.50	$233.50	$233.50
7 purchase totals =	$1,162.50		$1,253.5472	$1,253.54	$1,253.50	$1,253.60