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	$74.72	11.134%	$83.0393	$83.04	$83.05	$83.00
Purchase #2	$98.32	10.671%	$108.8117	$108.81	$108.80	$108.80
Purchase #3	$46.29	4.778%	$48.5017	$48.50	$48.50	$48.50
Purchase #4	$153.55	4.536%	$160.515	$160.52	$160.50	$160.50
Purchase #5	$149.89	6.477%	$159.5984	$159.60	$159.60	$159.60
Purchase #6	$226.76	13.653%	$257.7195	$257.72	$257.70	$257.70
Purchase #7	$250.48	3.131%	$258.3225	$258.32	$258.30	$258.30
7 purchase totals =	$1,000.01		$1,076.5081	$1,076.51	$1,076.45	$1,076.40