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	$48.75	11.669%	$54.4386	$54.44	$54.45	$54.40
Purchase #2	$247.80	3.387%	$256.193	$256.19	$256.20	$256.20
Purchase #3	$212.40	3.278%	$219.3625	$219.36	$219.35	$219.40
Purchase #4	$131.83	8.547%	$143.0975	$143.10	$143.10	$143.10
Purchase #5	$72.95	5.389%	$76.8813	$76.88	$76.90	$76.90
Purchase #6	$89.35	12.268%	$100.3115	$100.31	$100.30	$100.30
Purchase #7	$46.75	11.626%	$52.1852	$52.19	$52.20	$52.20
7 purchase totals =	$849.83		$902.4696	$902.47	$902.50	$902.50