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	$158.94	3.653%	$164.7461	$164.75	$164.75	$164.70
Purchase #2	$17.66	12.266%	$19.8262	$19.83	$19.85	$19.80
Purchase #3	$39.37	10.105%	$43.3483	$43.35	$43.35	$43.30
Purchase #4	$167.54	13.710%	$190.5097	$190.51	$190.50	$190.50
Purchase #5	$69.77	5.241%	$73.4266	$73.43	$73.45	$73.40
Purchase #6	$183.47	3.801%	$190.4437	$190.44	$190.45	$190.40
Purchase #7	$33.63	3.759%	$34.8942	$34.89	$34.90	$34.90
7 purchase totals =	$670.38		$717.1948	$717.20	$717.25	$717.00