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	$244.29	8.825%	$265.8486	$265.85	$265.85	$265.80
Purchase #2	$194.78	11.628%	$217.429	$217.43	$217.45	$217.40
Purchase #3	$38.31	12.705%	$43.1773	$43.18	$43.20	$43.20
Purchase #4	$131.35	10.846%	$145.5962	$145.60	$145.60	$145.60
Purchase #5	$103.45	8.667%	$112.416	$112.42	$112.40	$112.40
Purchase #6	$160.45	6.222%	$170.4332	$170.43	$170.45	$170.40
Purchase #7	$75.64	10.748%	$83.7698	$83.77	$83.75	$83.80
7 purchase totals =	$948.27		$1,038.6701	$1,038.68	$1,038.70	$1,038.60