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	$106.90	4.314%	$111.5117	$111.51	$111.50	$111.50
Purchase #2	$46.94	8.769%	$51.0562	$51.06	$51.05	$51.10
Purchase #3	$182.76	3.651%	$189.4326	$189.43	$189.45	$189.40
Purchase #4	$126.49	13.353%	$143.3802	$143.38	$143.40	$143.40
Purchase #5	$215.53	12.413%	$242.2837	$242.28	$242.30	$242.30
Purchase #6	$11.33	12.196%	$12.7118	$12.71	$12.70	$12.70
Purchase #7	$106.60	3.126%	$109.9323	$109.93	$109.95	$109.90
7 purchase totals =	$796.55		$860.3085	$860.30	$860.35	$860.30