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	$46.27	10.296%	$51.034	$51.03	$51.05	$51.00
Purchase #2	$52.78	6.180%	$56.0418	$56.04	$56.05	$56.00
Purchase #3	$59.78	9.371%	$65.382	$65.38	$65.40	$65.40
Purchase #4	$75.84	10.509%	$83.81	$83.81	$83.80	$83.80
Purchase #5	$90.56	13.670%	$102.9396	$102.94	$102.95	$102.90
Purchase #6	$208.67	3.403%	$215.771	$215.77	$215.75	$215.80
Purchase #7	$209.61	10.236%	$231.0657	$231.07	$231.05	$231.10
7 purchase totals =	$743.51		$806.0441	$806.04	$806.05	$806.00