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	$106.63	10.807%	$118.1535	$118.15	$118.15	$118.20
Purchase #2	$135.52	13.663%	$154.0361	$154.04	$154.05	$154.00
Purchase #3	$211.70	7.743%	$228.0919	$228.09	$228.10	$228.10
Purchase #4	$77.46	12.182%	$86.8962	$86.90	$86.90	$86.90
Purchase #5	$127.55	11.223%	$141.8649	$141.86	$141.85	$141.90
Purchase #6	$111.81	10.756%	$123.8363	$123.84	$123.85	$123.80
Purchase #7	$156.79	8.468%	$170.067	$170.07	$170.05	$170.10
7 purchase totals =	$927.46		$1,022.9459	$1,022.95	$1,022.95	$1,023.00