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	$60.86	10.315%	$67.1377	$67.14	$67.15	$67.10
Purchase #2	$80.51	6.346%	$85.6192	$85.62	$85.60	$85.60
Purchase #3	$128.87	13.712%	$146.5407	$146.54	$146.55	$146.50
Purchase #4	$225.79	8.348%	$244.6389	$244.64	$244.65	$244.60
Purchase #5	$179.71	10.243%	$198.1177	$198.12	$198.10	$198.10
Purchase #6	$241.31	7.845%	$260.2408	$260.24	$260.25	$260.20
Purchase #7	$67.70	5.563%	$71.4662	$71.47	$71.45	$71.50
7 purchase totals =	$984.75		$1,073.7612	$1,073.77	$1,073.75	$1,073.60