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	$30.43	12.138%	$34.1236	$34.12	$34.10	$34.10
Purchase #2	$16.78	12.731%	$18.9163	$18.92	$18.90	$18.90
Purchase #3	$60.42	3.721%	$62.6682	$62.67	$62.65	$62.70
Purchase #4	$180.90	8.865%	$196.9368	$196.94	$196.95	$196.90
Purchase #5	$95.33	5.551%	$100.6218	$100.62	$100.60	$100.60
Purchase #6	$166.59	13.660%	$189.3462	$189.35	$189.35	$189.30
Purchase #7	$146.64	7.670%	$157.8873	$157.89	$157.90	$157.90
7 purchase totals =	$697.09		$760.5002	$760.51	$760.45	$760.40