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	$211.82	3.178%	$218.5516	$218.55	$218.55	$218.60
Purchase #2	$15.51	5.530%	$16.3677	$16.37	$16.35	$16.40
Purchase #3	$72.55	8.304%	$78.5746	$78.57	$78.55	$78.60
Purchase #4	$11.72	6.493%	$12.481	$12.48	$12.50	$12.50
Purchase #5	$21.88	3.256%	$22.5924	$22.59	$22.60	$22.60
Purchase #6	$119.52	12.756%	$134.766	$134.77	$134.75	$134.80
Purchase #7	$31.50	3.311%	$32.543	$32.54	$32.55	$32.50
7 purchase totals =	$484.50		$515.8763	$515.87	$515.85	$516.00