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	$242.80	4.746%	$254.3233	$254.32	$254.30	$254.30
Purchase #2	$92.70	6.196%	$98.4437	$98.44	$98.45	$98.40
Purchase #3	$69.35	6.540%	$73.8855	$73.89	$73.90	$73.90
Purchase #4	$50.78	5.304%	$53.4734	$53.47	$53.45	$53.50
Purchase #5	$172.45	11.698%	$192.6232	$192.62	$192.60	$192.60
Purchase #6	$81.82	13.527%	$92.8878	$92.89	$92.90	$92.90
Purchase #7	$80.34	9.393%	$87.8863	$87.89	$87.90	$87.90
7 purchase totals =	$790.24		$853.5232	$853.52	$853.50	$853.50