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	$55.82	8.279%	$60.4413	$60.44	$60.45	$60.40
Purchase #2	$196.34	11.238%	$218.4047	$218.40	$218.40	$218.40
Purchase #3	$61.35	10.222%	$67.6212	$67.62	$67.60	$67.60
Purchase #4	$55.36	13.403%	$62.7799	$62.78	$62.80	$62.80
Purchase #5	$108.49	5.292%	$114.2313	$114.23	$114.25	$114.20
Purchase #6	$139.89	9.262%	$152.8466	$152.85	$152.85	$152.80
Purchase #7	$9.83	12.223%	$11.0315	$11.03	$11.05	$11.00
7 purchase totals =	$627.08		$687.3565	$687.35	$687.40	$687.20