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	$217.43	3.553%	$225.1553	$225.16	$225.15	$225.20
Purchase #2	$63.82	6.137%	$67.7366	$67.74	$67.75	$67.70
Purchase #3	$80.65	12.637%	$90.8417	$90.84	$90.85	$90.80
Purchase #4	$214.40	3.614%	$222.1484	$222.15	$222.15	$222.10
Purchase #5	$83.98	4.570%	$87.8179	$87.82	$87.80	$87.80
Purchase #6	$20.55	5.810%	$21.744	$21.74	$21.75	$21.70
Purchase #7	$136.87	5.646%	$144.5977	$144.60	$144.60	$144.60
7 purchase totals =	$817.70		$860.0416	$860.05	$860.05	$859.90