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	$206.82	12.147%	$231.9424	$231.94	$231.95	$231.90
Purchase #2	$73.55	12.645%	$82.8504	$82.85	$82.85	$82.90
Purchase #3	$59.79	4.771%	$62.6426	$62.64	$62.65	$62.60
Purchase #4	$213.79	10.786%	$236.8494	$236.85	$236.85	$236.80
Purchase #5	$17.91	11.732%	$20.0112	$20.01	$20.00	$20.00
Purchase #6	$145.96	9.260%	$159.4759	$159.48	$159.50	$159.50
Purchase #7	$81.90	13.306%	$92.7976	$92.80	$92.80	$92.80
7 purchase totals =	$799.72		$886.5695	$886.57	$886.60	$886.50