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	$12.40	5.294%	$13.0565	$13.06	$13.05	$13.10
Purchase #2	$33.32	9.338%	$36.4314	$36.43	$36.45	$36.40
Purchase #3	$26.47	6.752%	$28.2573	$28.26	$28.25	$28.30
Purchase #4	$80.78	10.172%	$88.9969	$89.00	$89.00	$89.00
Purchase #5	$230.31	11.367%	$256.4893	$256.49	$256.50	$256.50
Purchase #6	$178.76	9.835%	$196.341	$196.34	$196.35	$196.30
Purchase #7	$68.37	9.363%	$74.7715	$74.77	$74.75	$74.80
7 purchase totals =	$630.41		$694.3439	$694.35	$694.35	$694.40