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	$95.41	12.784%	$107.6072	$107.61	$107.60	$107.60
Purchase #2	$108.45	7.479%	$116.561	$116.56	$116.55	$116.60
Purchase #3	$115.98	8.176%	$125.4625	$125.46	$125.45	$125.50
Purchase #4	$78.37	9.626%	$85.9139	$85.91	$85.90	$85.90
Purchase #5	$18.56	11.373%	$20.6708	$20.67	$20.65	$20.70
Purchase #6	$109.74	8.135%	$118.6673	$118.67	$118.65	$118.70
Purchase #7	$100.72	10.669%	$111.4658	$111.47	$111.45	$111.50
7 purchase totals =	$627.23		$686.3485	$686.35	$686.25	$686.50