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	$63.68	7.131%	$68.221	$68.22	$68.20	$68.20
Purchase #2	$71.43	10.248%	$78.7501	$78.75	$78.75	$78.80
Purchase #3	$32.77	7.714%	$35.2979	$35.30	$35.30	$35.30
Purchase #4	$15.80	13.118%	$17.8726	$17.87	$17.85	$17.90
Purchase #5	$151.57	7.396%	$162.7801	$162.78	$162.80	$162.80
Purchase #6	$74.34	12.327%	$83.5039	$83.50	$83.50	$83.50
Purchase #7	$66.96	6.435%	$71.2689	$71.27	$71.25	$71.30
7 purchase totals =	$476.55		$517.6945	$517.69	$517.65	$517.80