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	$195.40	10.768%	$216.4407	$216.44	$216.45	$216.40
Purchase #2	$89.39	11.202%	$99.4035	$99.40	$99.40	$99.40
Purchase #3	$190.54	11.534%	$212.5169	$212.52	$212.50	$212.50
Purchase #4	$151.94	12.225%	$170.5147	$170.51	$170.50	$170.50
Purchase #5	$57.80	13.387%	$65.5377	$65.54	$65.55	$65.50
Purchase #6	$89.68	13.795%	$102.0514	$102.05	$102.05	$102.10
Purchase #7	$89.34	12.850%	$100.8202	$100.82	$100.80	$100.80
7 purchase totals =	$864.09		$967.2851	$967.28	$967.25	$967.20