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	$203.89	9.778%	$223.8264	$223.83	$223.85	$223.80
Purchase #2	$13.92	11.172%	$15.4751	$15.48	$15.50	$15.50
Purchase #3	$243.86	5.451%	$257.1528	$257.15	$257.15	$257.20
Purchase #4	$212.72	5.204%	$223.7899	$223.79	$223.80	$223.80
Purchase #5	$45.88	8.726%	$49.8835	$49.88	$49.90	$49.90
Purchase #6	$116.34	6.370%	$123.7509	$123.75	$123.75	$123.80
Purchase #7	$95.43	12.831%	$107.6746	$107.67	$107.65	$107.70
7 purchase totals =	$932.04		$1,001.5532	$1,001.55	$1,001.60	$1,001.70