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	$54.56	3.571%	$56.5083	$56.51	$56.50	$56.50
Purchase #2	$213.87	4.103%	$222.6451	$222.65	$222.65	$222.60
Purchase #3	$132.42	9.550%	$145.0661	$145.07	$145.05	$145.10
Purchase #4	$149.27	8.725%	$162.2938	$162.29	$162.30	$162.30
Purchase #5	$90.42	7.553%	$97.2494	$97.25	$97.25	$97.20
Purchase #6	$52.48	13.551%	$59.5916	$59.59	$59.60	$59.60
Purchase #7	$184.56	10.234%	$203.4479	$203.45	$203.45	$203.40
7 purchase totals =	$877.58		$946.8022	$946.81	$946.80	$946.70