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	$243.70	13.126%	$275.6881	$275.69	$275.70	$275.70
Purchase #2	$77.37	4.615%	$80.9406	$80.94	$80.95	$80.90
Purchase #3	$114.28	10.284%	$126.0326	$126.03	$126.05	$126.00
Purchase #4	$88.89	13.225%	$100.6457	$100.65	$100.65	$100.60
Purchase #5	$191.89	5.690%	$202.8085	$202.81	$202.80	$202.80
Purchase #6	$101.29	10.315%	$111.7381	$111.74	$111.75	$111.70
Purchase #7	$164.61	6.704%	$175.6455	$175.65	$175.65	$175.60
7 purchase totals =	$982.03		$1,073.4991	$1,073.51	$1,073.55	$1,073.30