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	$172.71	6.456%	$183.8602	$183.86	$183.85	$183.90
Purchase #2	$210.44	4.343%	$219.5794	$219.58	$219.60	$219.60
Purchase #3	$38.91	3.462%	$40.2571	$40.26	$40.25	$40.30
Purchase #4	$102.86	8.441%	$111.5424	$111.54	$111.55	$111.50
Purchase #5	$108.65	13.518%	$123.3373	$123.34	$123.35	$123.30
Purchase #6	$249.40	8.647%	$270.9656	$270.97	$270.95	$271.00
Purchase #7	$90.72	10.752%	$100.4742	$100.47	$100.45	$100.50
7 purchase totals =	$973.69		$1,050.0162	$1,050.02	$1,050.00	$1,050.10