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	$10.95	8.342%	$11.8634	$11.86	$11.85	$11.90
Purchase #2	$110.62	11.306%	$123.1267	$123.13	$123.15	$123.10
Purchase #3	$76.27	3.151%	$78.6733	$78.67	$78.65	$78.70
Purchase #4	$8.81	3.786%	$9.1435	$9.14	$9.15	$9.10
Purchase #5	$98.87	13.414%	$112.1324	$112.13	$112.15	$112.10
Purchase #6	$85.89	9.229%	$93.8168	$93.82	$93.80	$93.80
Purchase #7	$45.47	9.317%	$49.7064	$49.71	$49.70	$49.70
7 purchase totals =	$436.88		$478.4625	$478.46	$478.45	$478.40