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	$56.53	11.571%	$63.0711	$63.07	$63.05	$63.10
Purchase #2	$93.87	9.744%	$103.0167	$103.02	$103.00	$103.00
Purchase #3	$82.80	8.112%	$89.5167	$89.52	$89.50	$89.50
Purchase #4	$117.60	3.224%	$121.3914	$121.39	$121.40	$121.40
Purchase #5	$171.89	10.801%	$190.4558	$190.46	$190.45	$190.50
Purchase #6	$122.63	13.609%	$139.3187	$139.32	$139.30	$139.30
Purchase #7	$203.94	4.324%	$212.7584	$212.76	$212.75	$212.80
7 purchase totals =	$849.26		$919.5288	$919.54	$919.45	$919.60