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	$91.62	4.435%	$95.6833	$95.68	$95.70	$95.70
Purchase #2	$37.81	6.634%	$40.3183	$40.32	$40.30	$40.30
Purchase #3	$26.52	11.228%	$29.4977	$29.50	$29.50	$29.50
Purchase #4	$10.26	5.650%	$10.8397	$10.84	$10.85	$10.80
Purchase #5	$140.60	7.626%	$151.3222	$151.32	$151.30	$151.30
Purchase #6	$73.41	11.506%	$81.8566	$81.86	$81.85	$81.90
Purchase #7	$168.45	6.538%	$179.4633	$179.46	$179.45	$179.50
7 purchase totals =	$548.67		$588.9811	$588.98	$588.95	$589.00