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	$59.45	6.836%	$63.514	$63.51	$63.50	$63.50
Purchase #2	$52.41	12.709%	$59.0708	$59.07	$59.05	$59.10
Purchase #3	$244.35	5.137%	$256.9023	$256.90	$256.90	$256.90
Purchase #4	$224.32	13.699%	$255.0496	$255.05	$255.05	$255.00
Purchase #5	$134.45	13.777%	$152.9732	$152.97	$152.95	$153.00
Purchase #6	$165.64	5.795%	$175.2388	$175.24	$175.25	$175.20
Purchase #7	$233.81	11.249%	$260.1113	$260.11	$260.10	$260.10
7 purchase totals =	$1,114.43		$1,222.8600	$1,222.85	$1,222.80	$1,222.80