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	$172.74	11.517%	$192.6345	$192.63	$192.65	$192.60
Purchase #2	$132.72	3.426%	$137.267	$137.27	$137.25	$137.30
Purchase #3	$187.52	4.769%	$196.4628	$196.46	$196.45	$196.50
Purchase #4	$79.43	5.737%	$83.9869	$83.99	$84.00	$84.00
Purchase #5	$72.50	13.187%	$82.0606	$82.06	$82.05	$82.10
Purchase #6	$15.45	7.693%	$16.6386	$16.64	$16.65	$16.60
Purchase #7	$7.31	4.683%	$7.6523	$7.65	$7.65	$7.70
7 purchase totals =	$667.67		$716.7027	$716.70	$716.70	$716.80