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	$187.44	8.302%	$203.0013	$203.00	$203.00	$203.00
Purchase #2	$22.41	13.857%	$25.5154	$25.52	$25.50	$25.50
Purchase #3	$38.98	7.575%	$41.9327	$41.93	$41.95	$41.90
Purchase #4	$182.50	4.143%	$190.061	$190.06	$190.05	$190.10
Purchase #5	$101.93	9.667%	$111.7836	$111.78	$111.80	$111.80
Purchase #6	$240.71	6.558%	$256.4958	$256.50	$256.50	$256.50
Purchase #7	$122.46	8.522%	$132.896	$132.90	$132.90	$132.90
7 purchase totals =	$896.43		$961.6858	$961.69	$961.70	$961.70