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	$141.61	10.593%	$156.6107	$156.61	$156.60	$156.60
Purchase #2	$50.74	11.717%	$56.6852	$56.69	$56.70	$56.70
Purchase #3	$58.26	3.767%	$60.4547	$60.45	$60.45	$60.50
Purchase #4	$59.36	4.237%	$61.8751	$61.88	$61.90	$61.90
Purchase #5	$87.68	8.683%	$95.2933	$95.29	$95.30	$95.30
Purchase #6	$49.99	3.806%	$51.8926	$51.89	$51.90	$51.90
Purchase #7	$35.65	13.292%	$40.3886	$40.39	$40.40	$40.40
7 purchase totals =	$483.29		$523.2002	$523.20	$523.25	$523.30