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	$168.83	12.652%	$190.1904	$190.19	$190.20	$190.20
Purchase #2	$97.49	5.321%	$102.6774	$102.68	$102.70	$102.70
Purchase #3	$157.83	7.142%	$169.1022	$169.10	$169.10	$169.10
Purchase #4	$7.51	6.763%	$8.0179	$8.02	$8.00	$8.00
Purchase #5	$38.52	11.683%	$43.0203	$43.02	$43.00	$43.00
Purchase #6	$182.25	4.273%	$190.0375	$190.04	$190.05	$190.00
Purchase #7	$73.45	13.156%	$83.1131	$83.11	$83.10	$83.10
7 purchase totals =	$725.88		$786.1588	$786.16	$786.15	$786.10