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	$14.39	9.757%	$15.794	$15.79	$15.80	$15.80
Purchase #2	$82.37	4.106%	$85.7521	$85.75	$85.75	$85.80
Purchase #3	$95.70	3.630%	$99.1739	$99.17	$99.15	$99.20
Purchase #4	$86.87	12.666%	$97.873	$97.87	$97.85	$97.90
Purchase #5	$212.69	6.186%	$225.847	$225.85	$225.85	$225.80
Purchase #6	$117.40	5.215%	$123.5224	$123.52	$123.50	$123.50
Purchase #7	$155.92	7.597%	$167.7652	$167.77	$167.75	$167.80
7 purchase totals =	$765.34		$815.7276	$815.72	$815.65	$815.80