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	$21.92	9.155%	$23.9268	$23.93	$23.95	$23.90
Purchase #2	$127.62	10.789%	$141.3889	$141.39	$141.40	$141.40
Purchase #3	$60.59	6.166%	$64.326	$64.33	$64.35	$64.30
Purchase #4	$40.75	8.459%	$44.197	$44.20	$44.20	$44.20
Purchase #5	$69.85	4.390%	$72.9164	$72.92	$72.90	$72.90
Purchase #6	$179.49	5.236%	$188.8881	$188.89	$188.90	$188.90
Purchase #7	$173.80	9.778%	$190.7942	$190.79	$190.80	$190.80
7 purchase totals =	$674.02		$726.4374	$726.45	$726.50	$726.40