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	$132.77	8.551%	$144.1232	$144.12	$144.10	$144.10
Purchase #2	$228.64	5.636%	$241.5262	$241.53	$241.55	$241.50
Purchase #3	$158.93	6.854%	$169.8231	$169.82	$169.80	$169.80
Purchase #4	$118.80	13.221%	$134.5065	$134.51	$134.50	$134.50
Purchase #5	$85.67	7.845%	$92.3908	$92.39	$92.40	$92.40
Purchase #6	$77.61	10.843%	$86.0253	$86.03	$86.05	$86.00
Purchase #7	$132.53	6.794%	$141.5341	$141.53	$141.55	$141.50
7 purchase totals =	$934.95		$1,009.9292	$1,009.93	$1,009.95	$1,009.80