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	$82.27	11.671%	$91.8717	$91.87	$91.85	$91.90
Purchase #2	$238.29	7.507%	$256.1784	$256.18	$256.20	$256.20
Purchase #3	$137.95	5.359%	$145.3427	$145.34	$145.35	$145.30
Purchase #4	$187.83	9.194%	$205.0991	$205.10	$205.10	$205.10
Purchase #5	$141.98	11.214%	$157.9016	$157.90	$157.90	$157.90
Purchase #6	$9.31	8.264%	$10.0794	$10.08	$10.10	$10.10
Purchase #7	$131.87	9.684%	$144.6403	$144.64	$144.65	$144.60
7 purchase totals =	$929.50		$1,011.1132	$1,011.11	$1,011.15	$1,011.10