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	$158.90	13.328%	$180.0782	$180.08	$180.10	$180.10
Purchase #2	$190.31	5.274%	$200.3469	$200.35	$200.35	$200.30
Purchase #3	$74.66	3.202%	$77.0506	$77.05	$77.05	$77.10
Purchase #4	$108.90	8.267%	$117.9028	$117.90	$117.90	$117.90
Purchase #5	$218.63	6.262%	$232.3206	$232.32	$232.30	$232.30
Purchase #6	$27.89	13.291%	$31.5969	$31.60	$31.60	$31.60
Purchase #7	$211.58	6.624%	$225.5951	$225.60	$225.60	$225.60
7 purchase totals =	$990.87		$1,064.8911	$1,064.90	$1,064.90	$1,064.90