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	$104.38	6.787%	$111.4643	$111.46	$111.45	$111.50
Purchase #2	$39.82	10.789%	$44.1162	$44.12	$44.10	$44.10
Purchase #3	$242.52	11.287%	$269.8932	$269.89	$269.90	$269.90
Purchase #4	$100.60	13.160%	$113.839	$113.84	$113.85	$113.80
Purchase #5	$21.42	7.538%	$23.0346	$23.03	$23.05	$23.00
Purchase #6	$56.60	7.642%	$60.9254	$60.93	$60.95	$60.90
Purchase #7	$117.51	5.654%	$124.154	$124.15	$124.15	$124.20
7 purchase totals =	$682.85		$747.4267	$747.42	$747.45	$747.40