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	$63.47	11.195%	$70.5755	$70.58	$70.60	$70.60
Purchase #2	$179.65	8.679%	$195.2418	$195.24	$195.25	$195.20
Purchase #3	$250.40	13.172%	$283.3827	$283.38	$283.40	$283.40
Purchase #4	$118.49	4.544%	$123.8742	$123.87	$123.85	$123.90
Purchase #5	$162.38	13.865%	$184.894	$184.89	$184.90	$184.90
Purchase #6	$94.65	9.308%	$103.46	$103.46	$103.45	$103.50
Purchase #7	$76.85	8.265%	$83.2017	$83.20	$83.20	$83.20
7 purchase totals =	$945.89		$1,044.6299	$1,044.62	$1,044.65	$1,044.70