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	$9.86	8.188%	$10.6673	$10.67	$10.65	$10.70
Purchase #2	$153.57	9.108%	$167.5572	$167.56	$167.55	$167.60
Purchase #3	$103.52	10.276%	$114.1577	$114.16	$114.15	$114.20
Purchase #4	$56.33	13.761%	$64.0816	$64.08	$64.10	$64.10
Purchase #5	$152.28	13.207%	$172.3916	$172.39	$172.40	$172.40
Purchase #6	$59.46	10.639%	$65.7859	$65.79	$65.80	$65.80
Purchase #7	$202.47	12.519%	$227.8172	$227.82	$227.80	$227.80
7 purchase totals =	$737.49		$822.4585	$822.47	$822.45	$822.60