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	$184.48	8.464%	$200.0944	$200.09	$200.10	$200.10
Purchase #2	$173.30	9.527%	$189.8103	$189.81	$189.80	$189.80
Purchase #3	$67.93	12.611%	$76.4967	$76.50	$76.50	$76.50
Purchase #4	$193.42	3.463%	$200.1181	$200.12	$200.10	$200.10
Purchase #5	$41.57	4.540%	$43.4573	$43.46	$43.45	$43.50
Purchase #6	$15.84	4.754%	$16.593	$16.59	$16.60	$16.60
Purchase #7	$40.66	4.363%	$42.434	$42.43	$42.45	$42.40
7 purchase totals =	$717.20		$769.0038	$769.00	$769.00	$769.00