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	$200.88	5.602%	$212.1333	$212.13	$212.15	$212.10
Purchase #2	$219.92	5.284%	$231.5406	$231.54	$231.55	$231.50
Purchase #3	$78.63	9.282%	$85.9284	$85.93	$85.95	$85.90
Purchase #4	$10.95	8.528%	$11.8838	$11.88	$11.90	$11.90
Purchase #5	$87.69	3.184%	$90.482	$90.48	$90.50	$90.50
Purchase #6	$102.34	13.340%	$115.9922	$115.99	$116.00	$116.00
Purchase #7	$156.33	10.103%	$172.124	$172.12	$172.10	$172.10
7 purchase totals =	$856.74		$920.0843	$920.07	$920.15	$920.00