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	$68.69	4.384%	$71.7014	$71.70	$71.70	$71.70
Purchase #2	$64.41	3.381%	$66.5877	$66.59	$66.60	$66.60
Purchase #3	$228.69	7.505%	$245.8532	$245.85	$245.85	$245.90
Purchase #4	$80.91	6.293%	$86.0017	$86.00	$86.00	$86.00
Purchase #5	$19.85	10.106%	$21.856	$21.86	$21.85	$21.90
Purchase #6	$70.33	10.671%	$77.8349	$77.83	$77.85	$77.80
Purchase #7	$59.87	5.676%	$63.2682	$63.27	$63.25	$63.30
7 purchase totals =	$592.75		$633.1031	$633.10	$633.10	$633.20