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	$99.72	7.856%	$107.554	$107.55	$107.55	$107.60
Purchase #2	$29.96	5.265%	$31.5374	$31.54	$31.55	$31.50
Purchase #3	$222.29	10.697%	$246.0684	$246.07	$246.05	$246.10
Purchase #4	$62.54	13.777%	$71.1561	$71.16	$71.15	$71.20
Purchase #5	$75.77	12.625%	$85.336	$85.34	$85.35	$85.30
Purchase #6	$100.71	11.848%	$112.6421	$112.64	$112.65	$112.60
Purchase #7	$84.62	4.359%	$88.3086	$88.31	$88.30	$88.30
7 purchase totals =	$675.61		$742.6026	$742.61	$742.60	$742.60