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	$113.51	11.285%	$126.3196	$126.32	$126.30	$126.30
Purchase #2	$207.40	11.656%	$231.5745	$231.57	$231.55	$231.60
Purchase #3	$190.40	5.279%	$200.4512	$200.45	$200.45	$200.50
Purchase #4	$105.66	8.649%	$114.7985	$114.80	$114.80	$114.80
Purchase #5	$111.96	10.286%	$123.4762	$123.48	$123.50	$123.50
Purchase #6	$86.72	4.212%	$90.3726	$90.37	$90.35	$90.40
Purchase #7	$212.42	11.563%	$236.9821	$236.98	$237.00	$237.00
7 purchase totals =	$1,028.07		$1,123.9747	$1,123.97	$1,123.95	$1,124.10