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	$185.26	12.721%	$208.8269	$208.83	$208.85	$208.80
Purchase #2	$129.93	5.466%	$137.032	$137.03	$137.05	$137.00
Purchase #3	$153.87	4.575%	$160.9096	$160.91	$160.90	$160.90
Purchase #4	$102.87	8.664%	$111.7827	$111.78	$111.80	$111.80
Purchase #5	$97.45	7.753%	$105.0053	$105.01	$105.00	$105.00
Purchase #6	$223.30	10.194%	$246.0632	$246.06	$246.05	$246.10
Purchase #7	$74.54	11.204%	$82.8915	$82.89	$82.90	$82.90
7 purchase totals =	$967.22		$1,052.5112	$1,052.51	$1,052.55	$1,052.50