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	$175.81	6.500%	$187.2377	$187.24	$187.25	$187.20
Purchase #2	$235.51	8.294%	$255.0432	$255.04	$255.05	$255.00
Purchase #3	$215.50	11.849%	$241.0346	$241.03	$241.05	$241.00
Purchase #4	$171.39	11.863%	$191.722	$191.72	$191.70	$191.70
Purchase #5	$53.84	5.587%	$56.848	$56.85	$56.85	$56.80
Purchase #6	$99.83	8.649%	$108.4643	$108.46	$108.45	$108.50
Purchase #7	$99.94	12.705%	$112.6374	$112.64	$112.65	$112.60
7 purchase totals =	$1,051.82		$1,152.9872	$1,152.98	$1,153.00	$1,152.80