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	$13.57	6.863%	$14.5013	$14.50	$14.50	$14.50
Purchase #2	$56.56	9.103%	$61.7087	$61.71	$61.70	$61.70
Purchase #3	$177.48	13.133%	$200.7884	$200.79	$200.80	$200.80
Purchase #4	$112.44	13.737%	$127.8859	$127.89	$127.90	$127.90
Purchase #5	$87.72	6.652%	$93.5551	$93.56	$93.55	$93.60
Purchase #6	$126.39	5.542%	$133.3945	$133.39	$133.40	$133.40
Purchase #7	$90.67	9.823%	$99.5765	$99.58	$99.60	$99.60
7 purchase totals =	$664.83		$731.4104	$731.42	$731.45	$731.50