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	$135.77	11.233%	$151.021	$151.02	$151.00	$151.00
Purchase #2	$47.85	7.291%	$51.3387	$51.34	$51.35	$51.30
Purchase #3	$142.66	11.176%	$158.6037	$158.60	$158.60	$158.60
Purchase #4	$135.86	3.627%	$140.7876	$140.79	$140.80	$140.80
Purchase #5	$133.25	10.768%	$147.5984	$147.60	$147.60	$147.60
Purchase #6	$67.32	13.641%	$76.5031	$76.50	$76.50	$76.50
Purchase #7	$97.58	7.200%	$104.6058	$104.61	$104.60	$104.60
7 purchase totals =	$760.29		$830.4583	$830.46	$830.45	$830.40