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	$143.41	8.845%	$156.0946	$156.09	$156.10	$156.10
Purchase #2	$238.85	11.572%	$266.4897	$266.49	$266.50	$266.50
Purchase #3	$129.49	8.661%	$140.7051	$140.71	$140.70	$140.70
Purchase #4	$235.82	9.710%	$258.7181	$258.72	$258.70	$258.70
Purchase #5	$207.73	8.364%	$225.1045	$225.10	$225.10	$225.10
Purchase #6	$104.42	6.862%	$111.5853	$111.59	$111.60	$111.60
Purchase #7	$107.80	12.115%	$120.86	$120.86	$120.85	$120.90
7 purchase totals =	$1,167.52		$1,279.5573	$1,279.56	$1,279.55	$1,279.60