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	$116.27	9.804%	$127.6691	$127.67	$127.65	$127.70
Purchase #2	$39.66	6.341%	$42.1748	$42.17	$42.15	$42.20
Purchase #3	$74.82	5.148%	$78.6717	$78.67	$78.65	$78.70
Purchase #4	$20.47	7.444%	$21.9938	$21.99	$22.00	$22.00
Purchase #5	$205.82	10.233%	$226.8816	$226.88	$226.90	$226.90
Purchase #6	$89.90	5.272%	$94.6395	$94.64	$94.65	$94.60
Purchase #7	$13.25	4.181%	$13.804	$13.80	$13.80	$13.80
7 purchase totals =	$560.19		$605.8345	$605.82	$605.80	$605.90