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	$211.73	12.788%	$238.806	$238.81	$238.80	$238.80
Purchase #2	$62.85	7.537%	$67.587	$67.59	$67.60	$67.60
Purchase #3	$173.29	10.840%	$192.0746	$192.07	$192.05	$192.10
Purchase #4	$245.45	13.706%	$279.0914	$279.09	$279.10	$279.10
Purchase #5	$192.87	9.831%	$211.831	$211.83	$211.85	$211.80
Purchase #6	$9.53	8.384%	$10.329	$10.33	$10.35	$10.30
Purchase #7	$105.95	3.512%	$109.671	$109.67	$109.65	$109.70
7 purchase totals =	$1,001.67		$1,109.3900	$1,109.39	$1,109.40	$1,109.40