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	$42.27	5.208%	$44.4714	$44.47	$44.45	$44.50
Purchase #2	$29.89	5.824%	$31.6308	$31.63	$31.65	$31.60
Purchase #3	$89.60	11.737%	$100.1164	$100.12	$100.10	$100.10
Purchase #4	$38.63	8.835%	$42.043	$42.04	$42.05	$42.00
Purchase #5	$192.35	10.646%	$212.8276	$212.83	$212.85	$212.80
Purchase #6	$33.29	3.646%	$34.5038	$34.50	$34.50	$34.50
Purchase #7	$47.29	7.581%	$50.8751	$50.88	$50.90	$50.90
7 purchase totals =	$473.32		$516.4681	$516.47	$516.50	$516.40