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	$151.82	5.110%	$159.578	$159.58	$159.60	$159.60
Purchase #2	$177.67	11.745%	$198.5373	$198.54	$198.55	$198.50
Purchase #3	$166.89	8.369%	$180.857	$180.86	$180.85	$180.90
Purchase #4	$40.86	4.662%	$42.7649	$42.76	$42.75	$42.80
Purchase #5	$214.48	4.659%	$224.4726	$224.47	$224.45	$224.50
Purchase #6	$192.28	4.203%	$200.3615	$200.36	$200.35	$200.40
Purchase #7	$10.52	8.419%	$11.4057	$11.41	$11.40	$11.40
7 purchase totals =	$954.52		$1,017.9770	$1,017.98	$1,017.95	$1,018.10