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	$76.66	11.495%	$85.4721	$85.47	$85.45	$85.50
Purchase #2	$97.74	11.122%	$108.6106	$108.61	$108.60	$108.60
Purchase #3	$223.47	12.250%	$250.8451	$250.85	$250.85	$250.80
Purchase #4	$157.72	13.306%	$178.7062	$178.71	$178.70	$178.70
Purchase #5	$154.57	3.761%	$160.3834	$160.38	$160.40	$160.40
Purchase #6	$37.67	7.708%	$40.5736	$40.57	$40.55	$40.60
Purchase #7	$177.74	11.426%	$198.0486	$198.05	$198.05	$198.00
7 purchase totals =	$925.57		$1,022.6396	$1,022.64	$1,022.60	$1,022.60