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	$197.47	9.709%	$216.6424	$216.64	$216.65	$216.60
Purchase #2	$126.95	8.299%	$137.4856	$137.49	$137.50	$137.50
Purchase #3	$169.82	12.384%	$190.8505	$190.85	$190.85	$190.90
Purchase #4	$6.59	10.399%	$7.2753	$7.28	$7.30	$7.30
Purchase #5	$83.93	7.499%	$90.2239	$90.22	$90.20	$90.20
Purchase #6	$146.55	5.561%	$154.6996	$154.70	$154.70	$154.70
Purchase #7	$17.32	6.610%	$18.4649	$18.46	$18.45	$18.50
7 purchase totals =	$748.63		$815.6422	$815.64	$815.65	$815.70