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	$144.56	12.563%	$162.7211	$162.72	$162.70	$162.70
Purchase #2	$178.38	11.849%	$199.5162	$199.52	$199.50	$199.50
Purchase #3	$10.60	10.447%	$11.7074	$11.71	$11.70	$11.70
Purchase #4	$122.54	9.781%	$134.5256	$134.53	$134.55	$134.50
Purchase #5	$56.54	11.195%	$62.8697	$62.87	$62.85	$62.90
Purchase #6	$190.85	6.355%	$202.9785	$202.98	$203.00	$203.00
Purchase #7	$40.71	3.325%	$42.0636	$42.06	$42.05	$42.10
7 purchase totals =	$744.18		$816.3821	$816.39	$816.35	$816.40