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	$232.40	11.641%	$259.4537	$259.45	$259.45	$259.50
Purchase #2	$14.29	10.189%	$15.746	$15.75	$15.75	$15.70
Purchase #3	$149.85	3.813%	$155.5638	$155.56	$155.55	$155.60
Purchase #4	$150.75	11.753%	$168.4676	$168.47	$168.45	$168.50
Purchase #5	$68.51	6.143%	$72.7186	$72.72	$72.70	$72.70
Purchase #6	$169.81	7.208%	$182.0499	$182.05	$182.05	$182.00
Purchase #7	$243.81	5.849%	$258.0704	$258.07	$258.05	$258.10
7 purchase totals =	$1,029.42		$1,112.0700	$1,112.07	$1,112.00	$1,112.10