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	$129.27	11.103%	$143.6228	$143.62	$143.60	$143.60
Purchase #2	$7.92	5.808%	$8.38	$8.38	$8.40	$8.40
Purchase #3	$155.50	3.402%	$160.7901	$160.79	$160.80	$160.80
Purchase #4	$165.70	3.445%	$171.4084	$171.41	$171.40	$171.40
Purchase #5	$17.54	5.307%	$18.4708	$18.47	$18.45	$18.50
Purchase #6	$13.90	11.387%	$15.4828	$15.48	$15.50	$15.50
Purchase #7	$92.57	13.119%	$104.7143	$104.71	$104.70	$104.70
7 purchase totals =	$582.40		$622.8692	$622.86	$622.85	$622.90