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	$198.79	7.808%	$214.3115	$214.31	$214.30	$214.30
Purchase #2	$144.57	10.870%	$160.2848	$160.28	$160.30	$160.30
Purchase #3	$224.38	10.552%	$248.0566	$248.06	$248.05	$248.10
Purchase #4	$72.72	12.133%	$81.5431	$81.54	$81.55	$81.50
Purchase #5	$163.32	5.328%	$172.0217	$172.02	$172.00	$172.00
Purchase #6	$117.59	3.312%	$121.4846	$121.48	$121.50	$121.50
Purchase #7	$83.51	8.252%	$90.4012	$90.40	$90.40	$90.40
7 purchase totals =	$1,004.88		$1,088.1035	$1,088.09	$1,088.10	$1,088.10