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	$230.59	13.865%	$262.5613	$262.56	$262.55	$262.60
Purchase #2	$39.98	13.472%	$45.3661	$45.37	$45.35	$45.40
Purchase #3	$62.77	12.476%	$70.6012	$70.60	$70.60	$70.60
Purchase #4	$50.58	9.848%	$55.5611	$55.56	$55.55	$55.60
Purchase #5	$151.41	13.451%	$171.7762	$171.78	$171.80	$171.80
Purchase #6	$8.42	8.754%	$9.1571	$9.16	$9.15	$9.20
Purchase #7	$12.32	9.215%	$13.4553	$13.46	$13.45	$13.50
7 purchase totals =	$556.07		$628.4783	$628.49	$628.45	$628.70