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	$199.91	6.853%	$213.6098	$213.61	$213.60	$213.60
Purchase #2	$154.29	5.569%	$162.8824	$162.88	$162.90	$162.90
Purchase #3	$127.77	12.636%	$143.915	$143.92	$143.90	$143.90
Purchase #4	$127.44	8.335%	$138.0621	$138.06	$138.05	$138.10
Purchase #5	$82.76	8.335%	$89.658	$89.66	$89.65	$89.70
Purchase #6	$89.86	8.201%	$97.2294	$97.23	$97.25	$97.20
Purchase #7	$137.96	4.136%	$143.666	$143.67	$143.65	$143.70
7 purchase totals =	$919.99		$989.0227	$989.03	$989.00	$989.10