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	$59.38	4.176%	$61.8597	$61.86	$61.85	$61.90
Purchase #2	$34.94	5.694%	$36.9295	$36.93	$36.95	$36.90
Purchase #3	$87.96	12.841%	$99.2549	$99.25	$99.25	$99.30
Purchase #4	$238.90	11.413%	$266.1657	$266.17	$266.15	$266.20
Purchase #5	$138.68	3.714%	$143.8306	$143.83	$143.85	$143.80
Purchase #6	$28.71	10.715%	$31.7863	$31.79	$31.80	$31.80
Purchase #7	$198.57	5.718%	$209.9242	$209.92	$209.90	$209.90
7 purchase totals =	$787.14		$849.7509	$849.75	$849.75	$849.80