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	$56.99	8.183%	$61.6535	$61.65	$61.65	$61.70
Purchase #2	$73.71	6.587%	$78.5653	$78.57	$78.55	$78.60
Purchase #3	$136.39	11.810%	$152.4977	$152.50	$152.50	$152.50
Purchase #4	$93.92	13.856%	$106.9336	$106.93	$106.95	$106.90
Purchase #5	$178.82	9.861%	$196.4534	$196.45	$196.45	$196.50
Purchase #6	$231.63	3.359%	$239.4105	$239.41	$239.40	$239.40
Purchase #7	$81.35	7.596%	$87.5293	$87.53	$87.55	$87.50
7 purchase totals =	$852.81		$923.0433	$923.04	$923.05	$923.10