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	$82.82	5.401%	$87.2931	$87.29	$87.30	$87.30
Purchase #2	$133.91	11.180%	$148.8811	$148.88	$148.90	$148.90
Purchase #3	$143.86	8.648%	$156.301	$156.30	$156.30	$156.30
Purchase #4	$157.32	13.151%	$178.0092	$178.01	$178.00	$178.00
Purchase #5	$199.94	11.522%	$222.9771	$222.98	$223.00	$223.00
Purchase #6	$142.45	8.826%	$155.0226	$155.02	$155.00	$155.00
Purchase #7	$31.95	12.342%	$35.8933	$35.89	$35.90	$35.90
7 purchase totals =	$892.25		$984.3774	$984.37	$984.40	$984.40