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	$66.94	8.469%	$72.6091	$72.61	$72.60	$72.60
Purchase #2	$182.61	11.864%	$204.2749	$204.27	$204.25	$204.30
Purchase #3	$138.87	13.708%	$157.9063	$157.91	$157.90	$157.90
Purchase #4	$69.54	4.210%	$72.4676	$72.47	$72.45	$72.50
Purchase #5	$215.32	6.143%	$228.5471	$228.55	$228.55	$228.50
Purchase #6	$35.53	12.726%	$40.0515	$40.05	$40.05	$40.10
Purchase #7	$33.50	12.149%	$37.5699	$37.57	$37.55	$37.60
7 purchase totals =	$742.31		$813.4264	$813.43	$813.35	$813.50