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	$106.46	5.663%	$112.4888	$112.49	$112.50	$112.50
Purchase #2	$11.90	9.791%	$13.0651	$13.07	$13.05	$13.10
Purchase #3	$39.73	13.654%	$45.1547	$45.15	$45.15	$45.20
Purchase #4	$146.27	3.650%	$151.6089	$151.61	$151.60	$151.60
Purchase #5	$143.78	12.647%	$161.9639	$161.96	$161.95	$162.00
Purchase #6	$29.45	6.737%	$31.434	$31.43	$31.45	$31.40
Purchase #7	$47.25	3.275%	$48.7974	$48.80	$48.80	$48.80
7 purchase totals =	$524.84		$564.5128	$564.51	$564.50	$564.60