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	$250.51	7.531%	$269.3759	$269.38	$269.40	$269.40
Purchase #2	$37.60	7.717%	$40.5016	$40.50	$40.50	$40.50
Purchase #3	$247.89	13.701%	$281.8534	$281.85	$281.85	$281.90
Purchase #4	$23.50	5.453%	$24.7815	$24.78	$24.80	$24.80
Purchase #5	$150.69	5.197%	$158.5214	$158.52	$158.50	$158.50
Purchase #6	$9.42	6.646%	$10.0461	$10.05	$10.05	$10.00
Purchase #7	$213.44	4.224%	$222.4557	$222.46	$222.45	$222.50
7 purchase totals =	$933.05		$1,007.5356	$1,007.54	$1,007.55	$1,007.60