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	$106.63	11.477%	$118.8679	$118.87	$118.85	$118.90
Purchase #2	$211.27	5.351%	$222.5751	$222.58	$222.60	$222.60
Purchase #3	$39.43	3.713%	$40.894	$40.89	$40.90	$40.90
Purchase #4	$5.61	8.532%	$6.0886	$6.09	$6.10	$6.10
Purchase #5	$126.71	8.534%	$137.5234	$137.52	$137.50	$137.50
Purchase #6	$155.52	4.105%	$161.9041	$161.90	$161.90	$161.90
Purchase #7	$36.80	12.240%	$41.3043	$41.30	$41.30	$41.30
7 purchase totals =	$681.97		$729.1574	$729.15	$729.15	$729.20