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	$56.54	4.534%	$59.1035	$59.10	$59.10	$59.10
Purchase #2	$29.31	6.795%	$31.3016	$31.30	$31.30	$31.30
Purchase #3	$58.99	3.213%	$60.8853	$60.89	$60.90	$60.90
Purchase #4	$95.80	3.522%	$99.1741	$99.17	$99.15	$99.20
Purchase #5	$73.94	8.837%	$80.4741	$80.47	$80.45	$80.50
Purchase #6	$30.54	11.743%	$34.1263	$34.13	$34.15	$34.10
Purchase #7	$217.80	10.105%	$239.8087	$239.81	$239.80	$239.80
7 purchase totals =	$562.92		$604.8736	$604.87	$604.85	$604.90