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	$44.49	9.276%	$48.6169	$48.62	$48.60	$48.60
Purchase #2	$200.51	11.203%	$222.9731	$222.97	$222.95	$223.00
Purchase #3	$76.58	8.190%	$82.8519	$82.85	$82.85	$82.90
Purchase #4	$112.34	13.378%	$127.3688	$127.37	$127.35	$127.40
Purchase #5	$39.74	6.826%	$42.4527	$42.45	$42.45	$42.50
Purchase #6	$5.88	10.536%	$6.4995	$6.50	$6.50	$6.50
Purchase #7	$237.39	5.116%	$249.5349	$249.53	$249.55	$249.50
7 purchase totals =	$716.93		$780.2978	$780.29	$780.25	$780.40