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	$232.71	9.103%	$253.8936	$253.89	$253.90	$253.90
Purchase #2	$146.90	3.131%	$151.4994	$151.50	$151.50	$151.50
Purchase #3	$180.97	5.716%	$191.3142	$191.31	$191.30	$191.30
Purchase #4	$125.35	4.849%	$131.4282	$131.43	$131.45	$131.40
Purchase #5	$25.89	4.455%	$27.0434	$27.04	$27.05	$27.00
Purchase #6	$246.38	10.669%	$272.6663	$272.67	$272.65	$272.70
Purchase #7	$20.38	7.404%	$21.8889	$21.89	$21.90	$21.90
7 purchase totals =	$978.58		$1,049.7340	$1,049.73	$1,049.75	$1,049.70