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	$216.53	5.577%	$228.6059	$228.61	$228.60	$228.60
Purchase #2	$50.90	3.482%	$52.6723	$52.67	$52.65	$52.70
Purchase #3	$108.71	13.645%	$123.5435	$123.54	$123.55	$123.50
Purchase #4	$77.91	5.398%	$82.1156	$82.12	$82.10	$82.10
Purchase #5	$15.86	13.729%	$18.0374	$18.04	$18.05	$18.00
Purchase #6	$184.78	11.339%	$205.7322	$205.73	$205.75	$205.70
Purchase #7	$214.36	4.413%	$223.8197	$223.82	$223.80	$223.80
7 purchase totals =	$869.05		$934.5266	$934.53	$934.50	$934.40