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	$214.53	9.861%	$235.6848	$235.68	$235.70	$235.70
Purchase #2	$189.83	5.692%	$200.6351	$200.64	$200.65	$200.60
Purchase #3	$6.60	11.638%	$7.3681	$7.37	$7.35	$7.40
Purchase #4	$210.52	13.398%	$238.7255	$238.73	$238.75	$238.70
Purchase #5	$156.85	12.326%	$176.1833	$176.18	$176.20	$176.20
Purchase #6	$157.51	9.208%	$172.0135	$172.01	$172.00	$172.00
Purchase #7	$89.97	11.271%	$100.1105	$100.11	$100.10	$100.10
7 purchase totals =	$1,025.81		$1,130.7208	$1,130.72	$1,130.75	$1,130.70