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	$21.67	13.658%	$24.6297	$24.63	$24.65	$24.60
Purchase #2	$30.47	7.379%	$32.7184	$32.72	$32.70	$32.70
Purchase #3	$24.92	11.871%	$27.8783	$27.88	$27.90	$27.90
Purchase #4	$63.45	3.124%	$65.4322	$65.43	$65.45	$65.40
Purchase #5	$40.77	10.845%	$45.1915	$45.19	$45.20	$45.20
Purchase #6	$30.51	12.642%	$34.3671	$34.37	$34.35	$34.40
Purchase #7	$101.25	3.205%	$104.4951	$104.50	$104.50	$104.50
7 purchase totals =	$313.04		$334.7123	$334.72	$334.75	$334.70