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	$39.67	10.192%	$43.7132	$43.71	$43.70	$43.70
Purchase #2	$241.43	5.848%	$255.5488	$255.55	$255.55	$255.50
Purchase #3	$143.70	9.666%	$157.59	$157.59	$157.60	$157.60
Purchase #4	$52.38	3.129%	$54.019	$54.02	$54.00	$54.00
Purchase #5	$46.93	4.283%	$48.94	$48.94	$48.95	$48.90
Purchase #6	$47.39	4.374%	$49.4628	$49.46	$49.45	$49.50
Purchase #7	$153.81	11.318%	$171.2182	$171.22	$171.20	$171.20
7 purchase totals =	$725.31		$780.4920	$780.49	$780.45	$780.40