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	$192.72	13.389%	$218.5233	$218.52	$218.50	$218.50
Purchase #2	$149.38	8.357%	$161.8637	$161.86	$161.85	$161.90
Purchase #3	$160.54	12.778%	$181.0538	$181.05	$181.05	$181.10
Purchase #4	$39.36	5.119%	$41.3748	$41.37	$41.35	$41.40
Purchase #5	$162.35	13.679%	$184.5579	$184.56	$184.55	$184.60
Purchase #6	$32.70	4.248%	$34.0891	$34.09	$34.10	$34.10
Purchase #7	$168.50	7.473%	$181.092	$181.09	$181.10	$181.10
7 purchase totals =	$905.55		$1,002.5546	$1,002.54	$1,002.50	$1,002.70