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	$207.70	9.808%	$228.0712	$228.07	$228.05	$228.10
Purchase #2	$234.37	7.331%	$251.5517	$251.55	$251.55	$251.60
Purchase #3	$196.64	13.153%	$222.5041	$222.50	$222.50	$222.50
Purchase #4	$83.83	7.783%	$90.3545	$90.35	$90.35	$90.40
Purchase #5	$61.99	12.756%	$69.8974	$69.90	$69.90	$69.90
Purchase #6	$59.78	8.614%	$64.9294	$64.93	$64.95	$64.90
Purchase #7	$117.84	9.168%	$128.6436	$128.64	$128.65	$128.60
7 purchase totals =	$962.15		$1,055.9519	$1,055.94	$1,055.95	$1,056.00