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	$30.72	6.592%	$32.7451	$32.75	$32.75	$32.70
Purchase #2	$119.83	12.262%	$134.5236	$134.52	$134.50	$134.50
Purchase #3	$25.91	7.565%	$27.8701	$27.87	$27.85	$27.90
Purchase #4	$100.82	11.359%	$112.2721	$112.27	$112.25	$112.30
Purchase #5	$32.48	6.104%	$34.4626	$34.46	$34.45	$34.50
Purchase #6	$154.88	12.754%	$174.6334	$174.63	$174.65	$174.60
Purchase #7	$48.72	4.367%	$50.8476	$50.85	$50.85	$50.80
7 purchase totals =	$513.36		$567.3545	$567.35	$567.30	$567.30