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	$80.99	5.730%	$85.6307	$85.63	$85.65	$85.60
Purchase #2	$166.51	12.576%	$187.4503	$187.45	$187.45	$187.50
Purchase #3	$47.58	13.504%	$54.0052	$54.01	$54.00	$54.00
Purchase #4	$177.37	4.206%	$184.8302	$184.83	$184.85	$184.80
Purchase #5	$54.59	7.633%	$58.7569	$58.76	$58.75	$58.80
Purchase #6	$210.42	3.273%	$217.307	$217.31	$217.30	$217.30
Purchase #7	$90.84	9.516%	$99.4843	$99.48	$99.50	$99.50
7 purchase totals =	$828.30		$887.4646	$887.47	$887.50	$887.50