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	$114.95	11.186%	$127.8083	$127.81	$127.80	$127.80
Purchase #2	$28.77	13.313%	$32.6002	$32.60	$32.60	$32.60
Purchase #3	$17.78	3.578%	$18.4162	$18.42	$18.40	$18.40
Purchase #4	$125.25	12.536%	$140.9513	$140.95	$140.95	$141.00
Purchase #5	$47.93	8.152%	$51.8373	$51.84	$51.85	$51.80
Purchase #6	$137.64	9.458%	$150.658	$150.66	$150.65	$150.70
Purchase #7	$231.50	4.149%	$241.1049	$241.10	$241.10	$241.10
7 purchase totals =	$703.82		$763.3762	$763.38	$763.35	$763.40