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	$76.89	7.806%	$82.892	$82.89	$82.90	$82.90
Purchase #2	$190.54	5.822%	$201.6332	$201.63	$201.65	$201.60
Purchase #3	$105.44	5.637%	$111.3837	$111.38	$111.40	$111.40
Purchase #4	$158.47	10.141%	$174.5404	$174.54	$174.55	$174.50
Purchase #5	$144.86	6.744%	$154.6294	$154.63	$154.65	$154.60
Purchase #6	$200.84	6.553%	$214.001	$214.00	$214.00	$214.00
Purchase #7	$129.39	13.542%	$146.912	$146.91	$146.90	$146.90
7 purchase totals =	$1,006.43		$1,085.9917	$1,085.98	$1,086.05	$1,085.90