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	$83.55	13.229%	$94.6028	$94.60	$94.60	$94.60
Purchase #2	$118.47	6.786%	$126.5094	$126.51	$126.50	$126.50
Purchase #3	$154.74	5.283%	$162.9149	$162.91	$162.90	$162.90
Purchase #4	$19.27	10.323%	$21.2592	$21.26	$21.25	$21.30
Purchase #5	$118.27	4.548%	$123.6489	$123.65	$123.65	$123.60
Purchase #6	$187.62	4.514%	$196.0892	$196.09	$196.10	$196.10
Purchase #7	$87.48	6.393%	$93.0726	$93.07	$93.05	$93.10
7 purchase totals =	$769.40		$818.0970	$818.09	$818.05	$818.10