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	$232.90	13.375%	$264.0504	$264.05	$264.05	$264.10
Purchase #2	$36.31	12.793%	$40.9551	$40.96	$40.95	$41.00
Purchase #3	$56.63	12.131%	$63.4998	$63.50	$63.50	$63.50
Purchase #4	$190.82	12.146%	$213.997	$214.00	$214.00	$214.00
Purchase #5	$204.88	8.274%	$221.8318	$221.83	$221.85	$221.80
Purchase #6	$231.88	4.149%	$241.5007	$241.50	$241.50	$241.50
Purchase #7	$78.47	10.400%	$86.6309	$86.63	$86.65	$86.60
7 purchase totals =	$1,031.89		$1,132.4657	$1,132.47	$1,132.50	$1,132.50