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	$63.90	12.201%	$71.6964	$71.70	$71.70	$71.70
Purchase #2	$215.41	8.399%	$233.5023	$233.50	$233.50	$233.50
Purchase #3	$42.94	7.333%	$46.0888	$46.09	$46.10	$46.10
Purchase #4	$158.70	3.542%	$164.3212	$164.32	$164.30	$164.30
Purchase #5	$46.89	5.813%	$49.6157	$49.62	$49.60	$49.60
Purchase #6	$208.53	7.444%	$224.053	$224.05	$224.05	$224.10
Purchase #7	$75.77	3.405%	$78.35	$78.35	$78.35	$78.40
7 purchase totals =	$812.14		$867.6274	$867.63	$867.60	$867.70