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	$73.57	9.530%	$80.5812	$80.58	$80.60	$80.60
Purchase #2	$89.76	12.144%	$100.6605	$100.66	$100.65	$100.70
Purchase #3	$149.83	5.151%	$157.5477	$157.55	$157.55	$157.50
Purchase #4	$171.78	11.831%	$192.1033	$192.10	$192.10	$192.10
Purchase #5	$247.59	3.235%	$255.5995	$255.60	$255.60	$255.60
Purchase #6	$247.65	3.210%	$255.5996	$255.60	$255.60	$255.60
Purchase #7	$192.34	10.632%	$212.7896	$212.79	$212.80	$212.80
7 purchase totals =	$1,172.52		$1,254.8814	$1,254.88	$1,254.90	$1,254.90