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	$59.83	13.510%	$67.913	$67.91	$67.90	$67.90
Purchase #2	$103.60	7.732%	$111.6104	$111.61	$111.60	$111.60
Purchase #3	$118.70	6.189%	$126.0463	$126.05	$126.05	$126.00
Purchase #4	$179.33	8.636%	$194.8169	$194.82	$194.80	$194.80
Purchase #5	$15.63	7.560%	$16.8116	$16.81	$16.80	$16.80
Purchase #6	$250.95	8.317%	$271.8215	$271.82	$271.80	$271.80
Purchase #7	$215.42	6.560%	$229.5516	$229.55	$229.55	$229.60
7 purchase totals =	$943.46		$1,018.5713	$1,018.57	$1,018.50	$1,018.50