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	$72.76	10.545%	$80.4325	$80.43	$80.45	$80.40
Purchase #2	$67.59	10.702%	$74.8235	$74.82	$74.80	$74.80
Purchase #3	$36.85	13.439%	$41.8023	$41.80	$41.80	$41.80
Purchase #4	$207.53	11.611%	$231.6263	$231.63	$231.65	$231.60
Purchase #5	$212.67	4.128%	$221.449	$221.45	$221.45	$221.40
Purchase #6	$183.93	6.861%	$196.5494	$196.55	$196.55	$196.50
Purchase #7	$161.89	6.288%	$172.0696	$172.07	$172.05	$172.10
7 purchase totals =	$943.22		$1,018.7526	$1,018.75	$1,018.75	$1,018.60