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	$234.34	5.792%	$247.913	$247.91	$247.90	$247.90
Purchase #2	$213.40	4.595%	$223.2057	$223.21	$223.20	$223.20
Purchase #3	$204.68	13.103%	$231.4992	$231.50	$231.50	$231.50
Purchase #4	$168.57	7.198%	$180.7037	$180.70	$180.70	$180.70
Purchase #5	$170.97	11.168%	$190.0639	$190.06	$190.05	$190.10
Purchase #6	$152.31	13.429%	$172.7637	$172.76	$172.75	$172.80
Purchase #7	$77.78	10.354%	$85.8333	$85.83	$85.85	$85.80
7 purchase totals =	$1,222.05		$1,331.9825	$1,331.97	$1,331.95	$1,332.00