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	$215.48	13.507%	$244.5849	$244.58	$244.60	$244.60
Purchase #2	$194.32	4.531%	$203.1246	$203.12	$203.10	$203.10
Purchase #3	$123.78	8.516%	$134.3211	$134.32	$134.30	$134.30
Purchase #4	$112.25	6.527%	$119.5766	$119.58	$119.60	$119.60
Purchase #5	$210.46	4.484%	$219.897	$219.90	$219.90	$219.90
Purchase #6	$111.91	13.318%	$126.8142	$126.81	$126.80	$126.80
Purchase #7	$34.67	11.210%	$38.5565	$38.56	$38.55	$38.60
7 purchase totals =	$1,002.87		$1,086.8749	$1,086.87	$1,086.85	$1,086.90