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	$52.39	4.219%	$54.6003	$54.60	$54.60	$54.60
Purchase #2	$230.79	11.195%	$256.6269	$256.63	$256.65	$256.60
Purchase #3	$85.96	6.838%	$91.8379	$91.84	$91.85	$91.80
Purchase #4	$144.50	13.516%	$164.0306	$164.03	$164.05	$164.00
Purchase #5	$126.59	9.326%	$138.3958	$138.40	$138.40	$138.40
Purchase #6	$10.82	11.782%	$12.0948	$12.09	$12.10	$12.10
Purchase #7	$204.77	12.814%	$231.0092	$231.01	$231.00	$231.00
7 purchase totals =	$855.82		$948.5955	$948.60	$948.65	$948.50