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	$10.50	9.177%	$11.4636	$11.46	$11.45	$11.50
Purchase #2	$13.88	4.636%	$14.5235	$14.52	$14.50	$14.50
Purchase #3	$126.63	8.674%	$137.6139	$137.61	$137.60	$137.60
Purchase #4	$66.57	8.868%	$72.4734	$72.47	$72.45	$72.50
Purchase #5	$149.89	11.777%	$167.5425	$167.54	$167.55	$167.50
Purchase #6	$146.46	8.260%	$158.5576	$158.56	$158.55	$158.60
Purchase #7	$41.68	9.285%	$45.55	$45.55	$45.55	$45.60
7 purchase totals =	$555.61		$607.7245	$607.71	$607.65	$607.80