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	$69.68	10.714%	$77.1455	$77.15	$77.15	$77.10
Purchase #2	$235.77	6.787%	$251.7717	$251.77	$251.75	$251.80
Purchase #3	$85.76	10.133%	$94.4501	$94.45	$94.45	$94.50
Purchase #4	$54.70	4.123%	$56.9553	$56.96	$56.95	$57.00
Purchase #5	$204.81	5.344%	$215.755	$215.76	$215.75	$215.80
Purchase #6	$88.50	13.577%	$100.5156	$100.52	$100.50	$100.50
Purchase #7	$161.52	4.116%	$168.1682	$168.17	$168.15	$168.20
7 purchase totals =	$900.74		$964.7614	$964.78	$964.70	$964.90