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	$47.48	9.430%	$51.9574	$51.96	$51.95	$52.00
Purchase #2	$190.76	13.291%	$216.1139	$216.11	$216.10	$216.10
Purchase #3	$55.66	10.872%	$61.7114	$61.71	$61.70	$61.70
Purchase #4	$111.66	9.742%	$122.5379	$122.54	$122.55	$122.50
Purchase #5	$188.75	5.576%	$199.2747	$199.27	$199.25	$199.30
Purchase #6	$148.92	13.852%	$169.5484	$169.55	$169.55	$169.50
Purchase #7	$37.38	13.757%	$42.5224	$42.52	$42.50	$42.50
7 purchase totals =	$780.61		$863.6661	$863.66	$863.60	$863.60