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	$120.78	5.455%	$127.3685	$127.37	$127.35	$127.40
Purchase #2	$95.90	12.598%	$107.9815	$107.98	$108.00	$108.00
Purchase #3	$225.98	10.112%	$248.8311	$248.83	$248.85	$248.80
Purchase #4	$134.65	12.842%	$151.9418	$151.94	$151.95	$151.90
Purchase #5	$168.47	4.600%	$176.2196	$176.22	$176.20	$176.20
Purchase #6	$192.82	12.765%	$217.4335	$217.43	$217.45	$217.40
Purchase #7	$61.62	3.633%	$63.8587	$63.86	$63.85	$63.90
7 purchase totals =	$1,000.22		$1,093.6347	$1,093.63	$1,093.65	$1,093.60