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	$75.89	9.521%	$83.1155	$83.12	$83.10	$83.10
Purchase #2	$18.52	6.642%	$19.7501	$19.75	$19.75	$19.80
Purchase #3	$35.27	3.791%	$36.6071	$36.61	$36.60	$36.60
Purchase #4	$97.82	8.284%	$105.9234	$105.92	$105.90	$105.90
Purchase #5	$34.85	9.235%	$38.0684	$38.07	$38.05	$38.10
Purchase #6	$200.53	13.513%	$227.6276	$227.63	$227.65	$227.60
Purchase #7	$229.89	11.218%	$255.6791	$255.68	$255.70	$255.70
7 purchase totals =	$692.77		$766.7712	$766.78	$766.75	$766.80