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	$71.85	9.382%	$78.591	$78.59	$78.60	$78.60
Purchase #2	$14.52	7.683%	$15.6356	$15.64	$15.65	$15.60
Purchase #3	$206.63	12.351%	$232.1509	$232.15	$232.15	$232.20
Purchase #4	$36.67	13.679%	$41.6861	$41.69	$41.70	$41.70
Purchase #5	$136.89	6.849%	$146.2656	$146.27	$146.25	$146.30
Purchase #6	$78.64	13.582%	$89.3209	$89.32	$89.30	$89.30
Purchase #7	$69.82	3.482%	$72.2511	$72.25	$72.25	$72.30
7 purchase totals =	$615.02		$675.9012	$675.91	$675.90	$676.00