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	$31.40	13.693%	$35.6996	$35.70	$35.70	$35.70
Purchase #2	$17.63	10.434%	$19.4695	$19.47	$19.45	$19.50
Purchase #3	$188.72	3.666%	$195.6385	$195.64	$195.65	$195.60
Purchase #4	$31.73	13.105%	$35.8882	$35.89	$35.90	$35.90
Purchase #5	$187.78	4.387%	$196.0179	$196.02	$196.00	$196.00
Purchase #6	$66.93	9.292%	$73.1491	$73.15	$73.15	$73.10
Purchase #7	$40.67	7.182%	$43.5909	$43.59	$43.60	$43.60
7 purchase totals =	$564.86		$599.4537	$599.46	$599.45	$599.40