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	$187.93	9.306%	$205.4188	$205.42	$205.40	$205.40
Purchase #2	$77.55	3.351%	$80.1487	$80.15	$80.15	$80.10
Purchase #3	$59.86	7.674%	$64.4537	$64.45	$64.45	$64.50
Purchase #4	$126.85	5.549%	$133.8889	$133.89	$133.90	$133.90
Purchase #5	$191.34	11.628%	$213.589	$213.59	$213.60	$213.60
Purchase #6	$134.70	13.738%	$153.2051	$153.21	$153.20	$153.20
Purchase #7	$105.78	5.367%	$111.4572	$111.46	$111.45	$111.50
7 purchase totals =	$884.01		$962.1614	$962.17	$962.15	$962.20