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	$31.89	3.660%	$33.0572	$33.06	$33.05	$33.10
Purchase #2	$85.54	5.778%	$90.4825	$90.48	$90.50	$90.50
Purchase #3	$199.77	12.162%	$224.066	$224.07	$224.05	$224.10
Purchase #4	$122.72	8.838%	$133.566	$133.57	$133.55	$133.60
Purchase #5	$233.25	8.649%	$253.4238	$253.42	$253.40	$253.40
Purchase #6	$247.70	13.824%	$281.942	$281.94	$281.95	$281.90
Purchase #7	$95.52	11.822%	$106.8124	$106.81	$106.80	$106.80
7 purchase totals =	$1,016.39		$1,123.3499	$1,123.35	$1,123.30	$1,123.40