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	$90.97	8.847%	$99.0181	$99.02	$99.00	$99.00
Purchase #2	$84.94	5.700%	$89.7816	$89.78	$89.80	$89.80
Purchase #3	$34.43	8.385%	$37.317	$37.32	$37.30	$37.30
Purchase #4	$21.31	9.660%	$23.3685	$23.37	$23.35	$23.40
Purchase #5	$241.57	7.650%	$260.0501	$260.05	$260.05	$260.10
Purchase #6	$77.40	4.166%	$80.6245	$80.62	$80.60	$80.60
Purchase #7	$136.27	11.752%	$152.2845	$152.28	$152.30	$152.30
7 purchase totals =	$686.89		$742.4443	$742.44	$742.40	$742.50