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	$212.61	7.158%	$227.8286	$227.83	$227.85	$227.80
Purchase #2	$128.65	6.555%	$137.083	$137.08	$137.10	$137.10
Purchase #3	$99.25	12.776%	$111.9302	$111.93	$111.95	$111.90
Purchase #4	$168.72	5.753%	$178.4265	$178.43	$178.45	$178.40
Purchase #5	$201.73	4.191%	$210.1845	$210.18	$210.20	$210.20
Purchase #6	$225.75	13.233%	$255.6235	$255.62	$255.60	$255.60
Purchase #7	$143.49	3.766%	$148.8938	$148.89	$148.90	$148.90
7 purchase totals =	$1,180.20		$1,269.9701	$1,269.96	$1,270.05	$1,269.90