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	$44.96	5.303%	$47.3442	$47.34	$47.35	$47.30
Purchase #2	$127.34	7.186%	$136.4907	$136.49	$136.50	$136.50
Purchase #3	$114.34	8.256%	$123.7799	$123.78	$123.80	$123.80
Purchase #4	$53.60	4.340%	$55.9262	$55.93	$55.95	$55.90
Purchase #5	$11.59	10.401%	$12.7955	$12.80	$12.80	$12.80
Purchase #6	$132.97	10.308%	$146.6765	$146.68	$146.70	$146.70
Purchase #7	$152.77	7.788%	$164.6677	$164.67	$164.65	$164.70
7 purchase totals =	$637.57		$687.6807	$687.69	$687.75	$687.70