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	$83.93	5.175%	$88.2734	$88.27	$88.25	$88.30
Purchase #2	$89.86	3.167%	$92.7059	$92.71	$92.70	$92.70
Purchase #3	$92.83	11.778%	$103.7635	$103.76	$103.75	$103.80
Purchase #4	$222.98	8.361%	$241.6234	$241.62	$241.60	$241.60
Purchase #5	$100.32	6.866%	$107.208	$107.21	$107.20	$107.20
Purchase #6	$140.39	9.353%	$153.5207	$153.52	$153.50	$153.50
Purchase #7	$42.65	12.339%	$47.9126	$47.91	$47.90	$47.90
7 purchase totals =	$772.96		$835.0075	$835.00	$834.90	$835.00