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	$13.29	12.385%	$14.936	$14.94	$14.95	$14.90
Purchase #2	$50.54	3.401%	$52.2589	$52.26	$52.25	$52.30
Purchase #3	$100.29	11.656%	$111.9798	$111.98	$112.00	$112.00
Purchase #4	$245.95	8.352%	$266.4917	$266.49	$266.50	$266.50
Purchase #5	$73.30	5.649%	$77.4407	$77.44	$77.45	$77.40
Purchase #6	$134.48	10.448%	$148.5305	$148.53	$148.55	$148.50
Purchase #7	$168.89	10.655%	$186.8852	$186.89	$186.90	$186.90
7 purchase totals =	$786.74		$858.5228	$858.53	$858.60	$858.50