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	$157.84	9.137%	$172.2618	$172.26	$172.25	$172.30
Purchase #2	$217.43	11.240%	$241.8691	$241.87	$241.85	$241.90
Purchase #3	$101.84	10.638%	$112.6737	$112.67	$112.65	$112.70
Purchase #4	$145.57	10.534%	$160.9043	$160.90	$160.90	$160.90
Purchase #5	$77.59	9.662%	$85.0867	$85.09	$85.10	$85.10
Purchase #6	$102.96	9.695%	$112.942	$112.94	$112.95	$112.90
Purchase #7	$6.63	6.509%	$7.0615	$7.06	$7.05	$7.10
7 purchase totals =	$809.86		$892.7991	$892.79	$892.75	$892.90