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	$193.45	3.632%	$200.4761	$200.48	$200.50	$200.50
Purchase #2	$46.96	11.836%	$52.5182	$52.52	$52.50	$52.50
Purchase #3	$160.51	8.186%	$173.6493	$173.65	$173.65	$173.60
Purchase #4	$92.58	4.393%	$96.647	$96.65	$96.65	$96.60
Purchase #5	$37.72	3.137%	$38.9033	$38.90	$38.90	$38.90
Purchase #6	$223.43	10.533%	$246.9639	$246.96	$246.95	$247.00
Purchase #7	$192.40	4.252%	$200.5808	$200.58	$200.60	$200.60
7 purchase totals =	$947.05		$1,009.7386	$1,009.74	$1,009.75	$1,009.70