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	$240.43	6.634%	$256.3801	$256.38	$256.40	$256.40
Purchase #2	$221.53	12.140%	$248.4237	$248.42	$248.40	$248.40
Purchase #3	$100.71	4.570%	$105.3124	$105.31	$105.30	$105.30
Purchase #4	$155.54	11.724%	$173.7755	$173.78	$173.80	$173.80
Purchase #5	$188.83	5.450%	$199.1212	$199.12	$199.10	$199.10
Purchase #6	$82.37	3.376%	$85.1508	$85.15	$85.15	$85.20
Purchase #7	$47.84	12.554%	$53.8458	$53.85	$53.85	$53.80
7 purchase totals =	$1,037.25		$1,122.0095	$1,122.01	$1,122.00	$1,122.00