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	$231.94	13.358%	$262.9225	$262.92	$262.90	$262.90
Purchase #2	$104.72	8.336%	$113.4495	$113.45	$113.45	$113.40
Purchase #3	$76.85	5.509%	$81.0837	$81.08	$81.10	$81.10
Purchase #4	$153.52	9.440%	$168.0123	$168.01	$168.00	$168.00
Purchase #5	$74.96	11.290%	$83.423	$83.42	$83.40	$83.40
Purchase #6	$177.78	4.524%	$185.8228	$185.82	$185.80	$185.80
Purchase #7	$192.48	3.609%	$199.4266	$199.43	$199.45	$199.40
7 purchase totals =	$1,012.25		$1,094.1404	$1,094.13	$1,094.10	$1,094.00