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	$208.72	13.433%	$236.7574	$236.76	$236.75	$236.80
Purchase #2	$242.42	6.642%	$258.5215	$258.52	$258.50	$258.50
Purchase #3	$183.77	8.803%	$199.9473	$199.95	$199.95	$199.90
Purchase #4	$192.76	4.183%	$200.8232	$200.82	$200.80	$200.80
Purchase #5	$92.53	12.330%	$103.9389	$103.94	$103.95	$103.90
Purchase #6	$131.38	4.834%	$137.7309	$137.73	$137.75	$137.70
Purchase #7	$29.76	4.340%	$31.0516	$31.05	$31.05	$31.10
7 purchase totals =	$1,081.34		$1,168.7708	$1,168.77	$1,168.75	$1,168.70