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	$114.72	4.133%	$119.4614	$119.46	$119.45	$119.50
Purchase #2	$153.86	10.755%	$170.4076	$170.41	$170.40	$170.40
Purchase #3	$116.91	8.485%	$126.8298	$126.83	$126.85	$126.80
Purchase #4	$74.46	4.747%	$77.9946	$77.99	$78.00	$78.00
Purchase #5	$56.32	5.635%	$59.4936	$59.49	$59.50	$59.50
Purchase #6	$32.37	12.443%	$36.3978	$36.40	$36.40	$36.40
Purchase #7	$60.76	3.566%	$62.9267	$62.93	$62.95	$62.90
7 purchase totals =	$609.40		$653.5115	$653.51	$653.55	$653.50