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	$78.68	13.193%	$89.0603	$89.06	$89.05	$89.10
Purchase #2	$70.35	3.199%	$72.6005	$72.60	$72.60	$72.60
Purchase #3	$96.49	9.686%	$105.836	$105.84	$105.85	$105.80
Purchase #4	$15.71	10.579%	$17.372	$17.37	$17.35	$17.40
Purchase #5	$206.64	5.377%	$217.751	$217.75	$217.75	$217.80
Purchase #6	$241.32	11.346%	$268.7002	$268.70	$268.70	$268.70
Purchase #7	$177.95	4.275%	$185.5574	$185.56	$185.55	$185.60
7 purchase totals =	$887.14		$956.8774	$956.88	$956.85	$957.00