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	$60.27	12.724%	$67.9388	$67.94	$67.95	$67.90
Purchase #2	$52.81	11.837%	$59.0611	$59.06	$59.05	$59.10
Purchase #3	$133.78	7.450%	$143.7466	$143.75	$143.75	$143.70
Purchase #4	$181.43	4.646%	$189.8592	$189.86	$189.85	$189.90
Purchase #5	$183.29	9.578%	$200.8455	$200.85	$200.85	$200.80
Purchase #6	$179.42	8.564%	$194.7855	$194.79	$194.80	$194.80
Purchase #7	$247.89	12.841%	$279.7216	$279.72	$279.70	$279.70
7 purchase totals =	$1,038.89		$1,135.9583	$1,135.97	$1,135.95	$1,135.90