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	$126.64	3.561%	$131.1497	$131.15	$131.15	$131.10
Purchase #2	$163.50	4.413%	$170.7153	$170.72	$170.70	$170.70
Purchase #3	$43.64	10.449%	$48.1999	$48.20	$48.20	$48.20
Purchase #4	$202.65	11.849%	$226.662	$226.66	$226.65	$226.70
Purchase #5	$19.95	7.253%	$21.397	$21.40	$21.40	$21.40
Purchase #6	$130.53	11.503%	$145.5449	$145.54	$145.55	$145.50
Purchase #7	$173.85	13.282%	$196.9408	$196.94	$196.95	$196.90
7 purchase totals =	$860.76		$940.6096	$940.61	$940.60	$940.50