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	$114.45	7.821%	$123.4011	$123.40	$123.40	$123.40
Purchase #2	$135.47	3.451%	$140.1451	$140.15	$140.15	$140.10
Purchase #3	$93.87	12.698%	$105.7896	$105.79	$105.80	$105.80
Purchase #4	$7.62	13.220%	$8.6274	$8.63	$8.65	$8.60
Purchase #5	$105.90	11.259%	$117.8233	$117.82	$117.80	$117.80
Purchase #6	$49.69	4.496%	$51.9241	$51.92	$51.90	$51.90
Purchase #7	$160.34	5.166%	$168.6232	$168.62	$168.60	$168.60
7 purchase totals =	$667.34		$716.3338	$716.33	$716.30	$716.20