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	$233.78	8.854%	$254.4789	$254.48	$254.50	$254.50
Purchase #2	$47.37	11.660%	$52.8933	$52.89	$52.90	$52.90
Purchase #3	$243.78	12.657%	$274.6352	$274.64	$274.65	$274.60
Purchase #4	$13.88	8.172%	$15.0143	$15.01	$15.00	$15.00
Purchase #5	$99.50	10.536%	$109.9833	$109.98	$110.00	$110.00
Purchase #6	$241.46	5.460%	$254.6437	$254.64	$254.65	$254.60
Purchase #7	$55.32	8.260%	$59.8894	$59.89	$59.90	$59.90
7 purchase totals =	$935.09		$1,021.5381	$1,021.53	$1,021.60	$1,021.50