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	$92.43	12.722%	$104.1889	$104.19	$104.20	$104.20
Purchase #2	$39.99	6.839%	$42.7249	$42.72	$42.70	$42.70
Purchase #3	$115.90	12.676%	$130.5915	$130.59	$130.60	$130.60
Purchase #4	$37.45	7.263%	$40.17	$40.17	$40.15	$40.20
Purchase #5	$118.69	8.592%	$128.8878	$128.89	$128.90	$128.90
Purchase #6	$13.99	13.433%	$15.8693	$15.87	$15.85	$15.90
Purchase #7	$23.72	7.416%	$25.4791	$25.48	$25.50	$25.50
7 purchase totals =	$442.17		$487.9115	$487.91	$487.90	$488.00