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	$36.72	13.260%	$41.5891	$41.59	$41.60	$41.60
Purchase #2	$125.90	7.530%	$135.3803	$135.38	$135.40	$135.40
Purchase #3	$215.83	10.686%	$238.8936	$238.89	$238.90	$238.90
Purchase #4	$174.33	8.431%	$189.0278	$189.03	$189.05	$189.00
Purchase #5	$105.43	10.615%	$116.6214	$116.62	$116.60	$116.60
Purchase #6	$205.48	12.785%	$231.7506	$231.75	$231.75	$231.80
Purchase #7	$68.86	5.235%	$72.4648	$72.46	$72.45	$72.50
7 purchase totals =	$932.55		$1,025.7276	$1,025.72	$1,025.75	$1,025.80