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	$102.86	6.422%	$109.4657	$109.47	$109.45	$109.50
Purchase #2	$105.96	11.463%	$118.1062	$118.11	$118.10	$118.10
Purchase #3	$63.29	5.526%	$66.7874	$66.79	$66.80	$66.80
Purchase #4	$91.61	10.863%	$101.5616	$101.56	$101.55	$101.60
Purchase #5	$101.85	10.722%	$112.7704	$112.77	$112.75	$112.80
Purchase #6	$132.28	6.582%	$140.9867	$140.99	$141.00	$141.00
Purchase #7	$76.66	11.473%	$85.4552	$85.46	$85.45	$85.50
7 purchase totals =	$674.51		$735.1332	$735.15	$735.10	$735.30