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	$105.41	10.567%	$116.5487	$116.55	$116.55	$116.50
Purchase #2	$119.81	12.355%	$134.6125	$134.61	$134.60	$134.60
Purchase #3	$71.85	8.648%	$78.0636	$78.06	$78.05	$78.10
Purchase #4	$75.95	9.312%	$83.0225	$83.02	$83.00	$83.00
Purchase #5	$136.85	6.742%	$146.0764	$146.08	$146.10	$146.10
Purchase #6	$176.67	7.706%	$190.2842	$190.28	$190.30	$190.30
Purchase #7	$44.61	9.625%	$48.9037	$48.90	$48.90	$48.90
7 purchase totals =	$731.15		$797.5116	$797.50	$797.50	$797.50