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	$39.64	7.458%	$42.5964	$42.60	$42.60	$42.60
Purchase #2	$48.28	7.292%	$51.8006	$51.80	$51.80	$51.80
Purchase #3	$64.41	4.419%	$67.2563	$67.26	$67.25	$67.30
Purchase #4	$100.55	7.554%	$108.1455	$108.15	$108.15	$108.10
Purchase #5	$103.61	7.695%	$111.5828	$111.58	$111.60	$111.60
Purchase #6	$193.41	11.678%	$215.9964	$216.00	$216.00	$216.00
Purchase #7	$63.66	5.294%	$67.0302	$67.03	$67.05	$67.00
7 purchase totals =	$613.56		$664.4082	$664.42	$664.45	$664.40