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	$177.43	12.758%	$200.0665	$200.07	$200.05	$200.10
Purchase #2	$91.56	5.307%	$96.4191	$96.42	$96.40	$96.40
Purchase #3	$19.46	9.383%	$21.2859	$21.29	$21.30	$21.30
Purchase #4	$160.78	8.243%	$174.0331	$174.03	$174.05	$174.00
Purchase #5	$85.81	13.382%	$97.2931	$97.29	$97.30	$97.30
Purchase #6	$69.85	3.444%	$72.2556	$72.26	$72.25	$72.30
Purchase #7	$190.78	9.246%	$208.4195	$208.42	$208.40	$208.40
7 purchase totals =	$795.67		$869.7728	$869.78	$869.75	$869.80