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	$212.54	3.526%	$220.0342	$220.03	$220.05	$220.00
Purchase #2	$72.38	11.462%	$80.6762	$80.68	$80.70	$80.70
Purchase #3	$218.33	6.639%	$232.8249	$232.82	$232.80	$232.80
Purchase #4	$95.28	4.328%	$99.4037	$99.40	$99.40	$99.40
Purchase #5	$55.56	12.480%	$62.4939	$62.49	$62.50	$62.50
Purchase #6	$177.94	10.449%	$196.533	$196.53	$196.55	$196.50
Purchase #7	$138.42	4.509%	$144.6614	$144.66	$144.65	$144.70
7 purchase totals =	$970.45		$1,036.6273	$1,036.61	$1,036.65	$1,036.60