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	$133.75	10.725%	$148.0947	$148.09	$148.10	$148.10
Purchase #2	$208.42	13.859%	$237.3049	$237.30	$237.30	$237.30
Purchase #3	$158.99	7.372%	$170.7107	$170.71	$170.70	$170.70
Purchase #4	$158.97	3.472%	$164.4894	$164.49	$164.50	$164.50
Purchase #5	$52.92	12.387%	$59.4752	$59.48	$59.50	$59.50
Purchase #6	$70.91	13.429%	$80.4325	$80.43	$80.45	$80.40
Purchase #7	$28.97	8.802%	$31.5199	$31.52	$31.50	$31.50
7 purchase totals =	$812.93		$892.0273	$892.02	$892.05	$892.00