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	$83.42	13.426%	$94.62	$94.62	$94.60	$94.60
Purchase #2	$71.81	7.358%	$77.0938	$77.09	$77.10	$77.10
Purchase #3	$233.41	12.484%	$262.5489	$262.55	$262.55	$262.50
Purchase #4	$208.72	3.233%	$215.4679	$215.47	$215.45	$215.50
Purchase #5	$190.89	13.428%	$216.5227	$216.52	$216.50	$216.50
Purchase #6	$115.61	13.346%	$131.0393	$131.04	$131.05	$131.00
Purchase #7	$45.43	8.844%	$49.4478	$49.45	$49.45	$49.40
7 purchase totals =	$949.29		$1,046.7404	$1,046.74	$1,046.70	$1,046.60