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	$191.43	3.109%	$197.3816	$197.38	$197.40	$197.40
Purchase #2	$177.80	12.144%	$199.392	$199.39	$199.40	$199.40
Purchase #3	$141.43	5.271%	$148.8848	$148.88	$148.90	$148.90
Purchase #4	$208.72	3.218%	$215.4366	$215.44	$215.45	$215.40
Purchase #5	$78.49	4.528%	$82.044	$82.04	$82.05	$82.00
Purchase #6	$95.47	5.549%	$100.7676	$100.77	$100.75	$100.80
Purchase #7	$18.67	6.752%	$19.9306	$19.93	$19.95	$19.90
7 purchase totals =	$912.01		$963.8372	$963.83	$963.90	$963.80