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	$48.26	13.860%	$54.9488	$54.95	$54.95	$54.90
Purchase #2	$116.80	9.617%	$128.0327	$128.03	$128.05	$128.00
Purchase #3	$48.29	8.577%	$52.4318	$52.43	$52.45	$52.40
Purchase #4	$54.56	13.367%	$61.853	$61.85	$61.85	$61.90
Purchase #5	$15.89	12.228%	$17.833	$17.83	$17.85	$17.80
Purchase #6	$68.30	12.843%	$77.0718	$77.07	$77.05	$77.10
Purchase #7	$160.78	7.864%	$173.4237	$173.42	$173.40	$173.40
7 purchase totals =	$512.88		$565.5948	$565.58	$565.60	$565.50