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	$163.49	11.702%	$182.6216	$182.62	$182.60	$182.60
Purchase #2	$95.27	4.246%	$99.3152	$99.32	$99.30	$99.30
Purchase #3	$120.91	8.771%	$131.515	$131.52	$131.50	$131.50
Purchase #4	$183.80	5.575%	$194.0469	$194.05	$194.05	$194.00
Purchase #5	$69.61	4.318%	$72.6158	$72.62	$72.60	$72.60
Purchase #6	$103.90	4.394%	$108.4654	$108.47	$108.45	$108.50
Purchase #7	$154.56	10.770%	$171.2061	$171.21	$171.20	$171.20
7 purchase totals =	$891.54		$959.7860	$959.81	$959.70	$959.70