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	$61.97	8.745%	$67.3893	$67.39	$67.40	$67.40
Purchase #2	$34.60	7.204%	$37.0926	$37.09	$37.10	$37.10
Purchase #3	$51.80	5.542%	$54.6708	$54.67	$54.65	$54.70
Purchase #4	$246.27	13.467%	$279.4352	$279.44	$279.45	$279.40
Purchase #5	$214.55	12.754%	$241.9137	$241.91	$241.90	$241.90
Purchase #6	$174.48	12.593%	$196.4523	$196.45	$196.45	$196.50
Purchase #7	$182.33	12.672%	$205.4349	$205.43	$205.45	$205.40
7 purchase totals =	$966.00		$1,082.3888	$1,082.38	$1,082.40	$1,082.40