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	$222.83	8.193%	$241.0865	$241.09	$241.10	$241.10
Purchase #2	$186.77	5.239%	$196.5549	$196.55	$196.55	$196.60
Purchase #3	$205.75	7.845%	$221.8911	$221.89	$221.90	$221.90
Purchase #4	$10.56	9.693%	$11.5836	$11.58	$11.60	$11.60
Purchase #5	$184.49	12.624%	$207.78	$207.78	$207.80	$207.80
Purchase #6	$110.89	11.731%	$123.8985	$123.90	$123.90	$123.90
Purchase #7	$218.68	4.225%	$227.9192	$227.92	$227.90	$227.90
7 purchase totals =	$1,139.97		$1,230.7138	$1,230.71	$1,230.75	$1,230.80