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	$9.83	7.863%	$10.6029	$10.60	$10.60	$10.60
Purchase #2	$82.38	4.773%	$86.312	$86.31	$86.30	$86.30
Purchase #3	$220.49	11.116%	$244.9997	$245.00	$245.00	$245.00
Purchase #4	$112.55	4.763%	$117.9108	$117.91	$117.90	$117.90
Purchase #5	$51.37	7.186%	$55.0614	$55.06	$55.05	$55.10
Purchase #6	$100.94	4.674%	$105.6579	$105.66	$105.65	$105.70
Purchase #7	$174.44	9.462%	$190.9455	$190.95	$190.95	$190.90
7 purchase totals =	$752.00		$811.4902	$811.49	$811.45	$811.50