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	$114.31	10.479%	$126.2885	$126.29	$126.30	$126.30
Purchase #2	$207.83	13.866%	$236.6477	$236.65	$236.65	$236.60
Purchase #3	$67.27	6.167%	$71.4185	$71.42	$71.40	$71.40
Purchase #4	$10.58	12.408%	$11.8928	$11.89	$11.90	$11.90
Purchase #5	$55.32	11.167%	$61.4976	$61.50	$61.50	$61.50
Purchase #6	$167.85	6.390%	$178.5756	$178.58	$178.60	$178.60
Purchase #7	$29.45	5.556%	$31.0862	$31.09	$31.10	$31.10
7 purchase totals =	$652.61		$717.4069	$717.42	$717.45	$717.40