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	$187.73	4.713%	$196.5777	$196.58	$196.60	$196.60
Purchase #2	$169.96	11.590%	$189.6584	$189.66	$189.65	$189.70
Purchase #3	$14.97	3.518%	$15.4966	$15.50	$15.50	$15.50
Purchase #4	$99.46	9.412%	$108.8212	$108.82	$108.80	$108.80
Purchase #5	$156.45	12.425%	$175.8889	$175.89	$175.90	$175.90
Purchase #6	$119.51	12.813%	$134.8228	$134.82	$134.80	$134.80
Purchase #7	$138.47	3.563%	$143.4037	$143.40	$143.40	$143.40
7 purchase totals =	$886.55		$964.6693	$964.67	$964.65	$964.70