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	$37.57	10.748%	$41.608	$41.61	$41.60	$41.60
Purchase #2	$35.56	3.766%	$36.8992	$36.90	$36.90	$36.90
Purchase #3	$172.66	13.770%	$196.4353	$196.44	$196.45	$196.40
Purchase #4	$199.40	4.553%	$208.4787	$208.48	$208.50	$208.50
Purchase #5	$106.61	4.794%	$111.7209	$111.72	$111.70	$111.70
Purchase #6	$156.85	13.521%	$178.0577	$178.06	$178.05	$178.10
Purchase #7	$194.98	12.530%	$219.411	$219.41	$219.40	$219.40
7 purchase totals =	$903.63		$992.6108	$992.62	$992.60	$992.60