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	$211.48	5.598%	$223.3187	$223.32	$223.30	$223.30
Purchase #2	$148.38	5.833%	$157.035	$157.04	$157.05	$157.00
Purchase #3	$197.82	12.128%	$221.8116	$221.81	$221.80	$221.80
Purchase #4	$83.39	7.806%	$89.8994	$89.90	$89.90	$89.90
Purchase #5	$37.94	7.807%	$40.902	$40.90	$40.90	$40.90
Purchase #6	$65.28	9.530%	$71.5012	$71.50	$71.50	$71.50
Purchase #7	$242.55	5.492%	$255.8708	$255.87	$255.85	$255.90
7 purchase totals =	$986.84		$1,060.3387	$1,060.34	$1,060.30	$1,060.30