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	$100.32	13.868%	$114.2324	$114.23	$114.25	$114.20
Purchase #2	$129.94	12.296%	$145.9174	$145.92	$145.90	$145.90
Purchase #3	$89.85	11.843%	$100.4909	$100.49	$100.50	$100.50
Purchase #4	$127.88	13.803%	$145.5313	$145.53	$145.55	$145.50
Purchase #5	$63.58	11.473%	$70.8745	$70.87	$70.85	$70.90
Purchase #6	$110.93	13.460%	$125.8612	$125.86	$125.85	$125.90
Purchase #7	$105.32	13.580%	$119.6225	$119.62	$119.60	$119.60
7 purchase totals =	$727.82		$822.5302	$822.52	$822.50	$822.50