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	$175.93	11.784%	$196.6616	$196.66	$196.65	$196.70
Purchase #2	$152.55	5.834%	$161.4498	$161.45	$161.45	$161.40
Purchase #3	$7.73	8.851%	$8.4142	$8.41	$8.40	$8.40
Purchase #4	$41.55	3.617%	$43.0529	$43.05	$43.05	$43.10
Purchase #5	$29.68	13.183%	$33.5927	$33.59	$33.60	$33.60
Purchase #6	$192.82	13.382%	$218.6232	$218.62	$218.60	$218.60
Purchase #7	$138.60	10.677%	$153.3983	$153.40	$153.40	$153.40
7 purchase totals =	$738.86		$815.1927	$815.18	$815.15	$815.20