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	$214.89	12.695%	$242.1703	$242.17	$242.15	$242.20
Purchase #2	$46.25	3.534%	$47.8845	$47.88	$47.90	$47.90
Purchase #3	$100.83	8.141%	$109.0386	$109.04	$109.05	$109.00
Purchase #4	$247.25	6.660%	$263.7169	$263.72	$263.70	$263.70
Purchase #5	$98.71	11.402%	$109.9649	$109.96	$109.95	$110.00
Purchase #6	$63.58	12.770%	$71.6992	$71.70	$71.70	$71.70
Purchase #7	$231.65	4.396%	$241.8333	$241.83	$241.85	$241.80
7 purchase totals =	$1,003.16		$1,086.3077	$1,086.30	$1,086.30	$1,086.30