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	$168.67	9.174%	$184.1438	$184.14	$184.15	$184.10
Purchase #2	$83.32	8.720%	$90.5855	$90.59	$90.60	$90.60
Purchase #3	$129.38	3.576%	$134.0066	$134.01	$134.00	$134.00
Purchase #4	$112.80	6.215%	$119.8105	$119.81	$119.80	$119.80
Purchase #5	$219.56	10.466%	$242.5391	$242.54	$242.55	$242.50
Purchase #6	$184.29	13.758%	$209.6446	$209.64	$209.65	$209.60
Purchase #7	$47.72	7.143%	$51.1286	$51.13	$51.15	$51.10
7 purchase totals =	$945.74		$1,031.8587	$1,031.86	$1,031.90	$1,031.70