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	$200.55	4.123%	$208.8187	$208.82	$208.80	$208.80
Purchase #2	$243.88	11.471%	$271.8555	$271.86	$271.85	$271.90
Purchase #3	$150.81	7.186%	$161.6472	$161.65	$161.65	$161.60
Purchase #4	$166.48	5.655%	$175.8944	$175.89	$175.90	$175.90
Purchase #5	$40.39	4.634%	$42.2617	$42.26	$42.25	$42.30
Purchase #6	$160.34	10.632%	$177.3873	$177.39	$177.40	$177.40
Purchase #7	$17.64	5.315%	$18.5776	$18.58	$18.60	$18.60
7 purchase totals =	$980.09		$1,056.4424	$1,056.45	$1,056.45	$1,056.50