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	$21.42	4.309%	$22.343	$22.34	$22.35	$22.30
Purchase #2	$38.81	13.304%	$43.9733	$43.97	$43.95	$44.00
Purchase #3	$200.60	10.396%	$221.4544	$221.45	$221.45	$221.50
Purchase #4	$233.70	13.638%	$265.572	$265.57	$265.55	$265.60
Purchase #5	$187.40	6.679%	$199.9164	$199.92	$199.90	$199.90
Purchase #6	$161.70	12.512%	$181.9319	$181.93	$181.95	$181.90
Purchase #7	$40.38	6.723%	$43.0947	$43.09	$43.10	$43.10
7 purchase totals =	$884.01		$978.2857	$978.27	$978.25	$978.30