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	$30.57	7.536%	$32.8738	$32.87	$32.85	$32.90
Purchase #2	$100.70	5.658%	$106.3976	$106.40	$106.40	$106.40
Purchase #3	$120.68	5.271%	$127.041	$127.04	$127.05	$127.00
Purchase #4	$32.64	4.429%	$34.0856	$34.09	$34.10	$34.10
Purchase #5	$79.67	12.389%	$89.5403	$89.54	$89.55	$89.50
Purchase #6	$173.73	10.436%	$191.8605	$191.86	$191.85	$191.90
Purchase #7	$43.47	8.706%	$47.2545	$47.25	$47.25	$47.30
7 purchase totals =	$581.46		$629.0533	$629.05	$629.05	$629.10