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	$159.32	13.550%	$180.9079	$180.91	$180.90	$180.90
Purchase #2	$166.72	8.682%	$181.1946	$181.19	$181.20	$181.20
Purchase #3	$232.66	10.698%	$257.55	$257.55	$257.55	$257.60
Purchase #4	$138.72	10.189%	$152.8542	$152.85	$152.85	$152.90
Purchase #5	$72.93	3.565%	$75.53	$75.53	$75.55	$75.50
Purchase #6	$70.89	8.626%	$77.005	$77.01	$77.00	$77.00
Purchase #7	$91.25	13.376%	$103.4556	$103.46	$103.45	$103.50
7 purchase totals =	$932.49		$1,028.4973	$1,028.50	$1,028.50	$1,028.60