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	$152.52	13.304%	$172.8113	$172.81	$172.80	$172.80
Purchase #2	$176.89	10.294%	$195.0991	$195.10	$195.10	$195.10
Purchase #3	$81.94	5.691%	$86.6032	$86.60	$86.60	$86.60
Purchase #4	$104.69	11.472%	$116.7	$116.70	$116.70	$116.70
Purchase #5	$63.55	3.330%	$65.6662	$65.67	$65.65	$65.70
Purchase #6	$96.69	4.806%	$101.3369	$101.34	$101.35	$101.30
Purchase #7	$104.85	11.210%	$116.6037	$116.60	$116.60	$116.60
7 purchase totals =	$781.13		$854.8204	$854.82	$854.80	$854.80