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	$157.53	9.729%	$172.8561	$172.86	$172.85	$172.90
Purchase #2	$36.39	11.516%	$40.5807	$40.58	$40.60	$40.60
Purchase #3	$249.77	8.696%	$271.49	$271.49	$271.50	$271.50
Purchase #4	$44.75	6.471%	$47.6458	$47.65	$47.65	$47.60
Purchase #5	$126.89	7.683%	$136.639	$136.64	$136.65	$136.60
Purchase #6	$213.26	4.502%	$222.861	$222.86	$222.85	$222.90
Purchase #7	$125.31	6.133%	$132.9953	$133.00	$133.00	$133.00
7 purchase totals =	$953.90		$1,025.0679	$1,025.08	$1,025.10	$1,025.10