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	$192.59	4.285%	$200.8425	$200.84	$200.85	$200.80
Purchase #2	$49.91	7.333%	$53.5699	$53.57	$53.55	$53.60
Purchase #3	$74.58	13.561%	$84.6938	$84.69	$84.70	$84.70
Purchase #4	$48.52	11.417%	$54.0595	$54.06	$54.05	$54.10
Purchase #5	$29.54	6.723%	$31.526	$31.53	$31.55	$31.50
Purchase #6	$33.80	8.257%	$36.5909	$36.59	$36.60	$36.60
Purchase #7	$167.98	13.390%	$190.4725	$190.47	$190.45	$190.50
7 purchase totals =	$596.92		$651.7551	$651.75	$651.75	$651.80