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	$39.82	11.541%	$44.4156	$44.42	$44.40	$44.40
Purchase #2	$92.60	10.673%	$102.4832	$102.48	$102.50	$102.50
Purchase #3	$91.99	4.248%	$95.8977	$95.90	$95.90	$95.90
Purchase #4	$97.97	6.393%	$104.2332	$104.23	$104.25	$104.20
Purchase #5	$101.80	9.443%	$111.413	$111.41	$111.40	$111.40
Purchase #6	$134.40	7.306%	$144.2193	$144.22	$144.20	$144.20
Purchase #7	$121.79	9.112%	$132.8875	$132.89	$132.90	$132.90
7 purchase totals =	$680.37		$735.5495	$735.55	$735.55	$735.50