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	$101.34	5.650%	$107.0657	$107.07	$107.05	$107.10
Purchase #2	$139.77	3.560%	$144.7458	$144.75	$144.75	$144.70
Purchase #3	$35.90	11.267%	$39.9449	$39.94	$39.95	$39.90
Purchase #4	$85.58	5.702%	$90.4598	$90.46	$90.45	$90.50
Purchase #5	$14.35	12.510%	$16.1452	$16.15	$16.15	$16.10
Purchase #6	$76.53	11.660%	$85.4534	$85.45	$85.45	$85.50
Purchase #7	$242.60	6.377%	$258.0706	$258.07	$258.05	$258.10
7 purchase totals =	$696.07		$741.8854	$741.89	$741.85	$741.90