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	$176.70	13.542%	$200.6287	$200.63	$200.65	$200.60
Purchase #2	$241.46	10.373%	$266.5066	$266.51	$266.50	$266.50
Purchase #3	$250.50	6.153%	$265.9133	$265.91	$265.90	$265.90
Purchase #4	$98.62	10.349%	$108.8262	$108.83	$108.85	$108.80
Purchase #5	$21.69	11.608%	$24.2078	$24.21	$24.20	$24.20
Purchase #6	$100.58	11.395%	$112.0411	$112.04	$112.05	$112.00
Purchase #7	$35.26	12.182%	$39.5554	$39.56	$39.55	$39.60
7 purchase totals =	$924.81		$1,017.6791	$1,017.69	$1,017.70	$1,017.60