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	$145.67	13.223%	$164.9319	$164.93	$164.95	$164.90
Purchase #2	$87.84	12.766%	$99.0537	$99.05	$99.05	$99.10
Purchase #3	$111.52	5.450%	$117.5978	$117.60	$117.60	$117.60
Purchase #4	$132.48	6.221%	$140.7216	$140.72	$140.70	$140.70
Purchase #5	$190.95	13.571%	$216.8638	$216.86	$216.85	$216.90
Purchase #6	$89.71	9.556%	$98.2827	$98.28	$98.30	$98.30
Purchase #7	$118.88	7.682%	$128.0124	$128.01	$128.00	$128.00
7 purchase totals =	$877.05		$965.4639	$965.45	$965.45	$965.50