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	$32.72	3.346%	$33.8148	$33.81	$33.80	$33.80
Purchase #2	$55.92	13.785%	$63.6286	$63.63	$63.65	$63.60
Purchase #3	$50.56	5.182%	$53.18	$53.18	$53.20	$53.20
Purchase #4	$130.25	8.719%	$141.6065	$141.61	$141.60	$141.60
Purchase #5	$131.31	6.665%	$140.0618	$140.06	$140.05	$140.10
Purchase #6	$30.95	6.168%	$32.859	$32.86	$32.85	$32.90
Purchase #7	$88.26	13.171%	$99.8847	$99.88	$99.90	$99.90
7 purchase totals =	$519.97		$565.0354	$565.03	$565.05	$565.10