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	$54.54	9.192%	$59.5533	$59.55	$59.55	$59.60
Purchase #2	$22.89	6.388%	$24.3522	$24.35	$24.35	$24.40
Purchase #3	$13.86	11.455%	$15.4477	$15.45	$15.45	$15.40
Purchase #4	$39.50	7.842%	$42.5976	$42.60	$42.60	$42.60
Purchase #5	$204.86	8.510%	$222.2936	$222.29	$222.30	$222.30
Purchase #6	$231.47	9.521%	$253.5083	$253.51	$253.50	$253.50
Purchase #7	$146.31	6.463%	$155.766	$155.77	$155.75	$155.80
7 purchase totals =	$713.43		$773.5187	$773.52	$773.50	$773.60