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	$45.39	12.488%	$51.0583	$51.06	$51.05	$51.10
Purchase #2	$83.88	6.158%	$89.0453	$89.05	$89.05	$89.00
Purchase #3	$170.46	3.274%	$176.0409	$176.04	$176.05	$176.00
Purchase #4	$12.76	6.700%	$13.6149	$13.61	$13.60	$13.60
Purchase #5	$49.84	4.206%	$51.9363	$51.94	$51.95	$51.90
Purchase #6	$184.80	3.264%	$190.8319	$190.83	$190.85	$190.80
Purchase #7	$168.46	3.686%	$174.6694	$174.67	$174.65	$174.70
7 purchase totals =	$715.59		$747.1970	$747.20	$747.20	$747.10