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	$82.66	3.783%	$85.787	$85.79	$85.80	$85.80
Purchase #2	$76.81	6.426%	$81.7458	$81.75	$81.75	$81.70
Purchase #3	$93.54	6.452%	$99.5752	$99.58	$99.60	$99.60
Purchase #4	$128.51	12.498%	$144.5712	$144.57	$144.55	$144.60
Purchase #5	$113.50	6.752%	$121.1635	$121.16	$121.15	$121.20
Purchase #6	$208.49	8.403%	$226.0094	$226.01	$226.00	$226.00
Purchase #7	$131.38	7.716%	$141.5173	$141.52	$141.50	$141.50
7 purchase totals =	$834.89		$900.3694	$900.38	$900.35	$900.40