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	$101.83	9.528%	$111.5324	$111.53	$111.55	$111.50
Purchase #2	$102.89	8.379%	$111.5112	$111.51	$111.50	$111.50
Purchase #3	$162.38	8.518%	$176.2115	$176.21	$176.20	$176.20
Purchase #4	$148.97	6.520%	$158.6828	$158.68	$158.70	$158.70
Purchase #5	$5.51	13.224%	$6.2386	$6.24	$6.25	$6.20
Purchase #6	$47.27	8.672%	$51.3693	$51.37	$51.35	$51.40
Purchase #7	$204.37	13.254%	$231.4572	$231.46	$231.45	$231.50
7 purchase totals =	$773.22		$847.0030	$847.00	$847.00	$847.00