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	$111.26	10.864%	$123.3473	$123.35	$123.35	$123.30
Purchase #2	$116.63	5.414%	$122.9443	$122.94	$122.95	$122.90
Purchase #3	$246.78	6.729%	$263.3858	$263.39	$263.40	$263.40
Purchase #4	$62.61	8.328%	$67.8242	$67.82	$67.80	$67.80
Purchase #5	$119.52	7.224%	$128.1541	$128.15	$128.15	$128.20
Purchase #6	$112.45	9.468%	$123.0968	$123.10	$123.10	$123.10
Purchase #7	$64.33	8.565%	$69.8399	$69.84	$69.85	$69.80
7 purchase totals =	$833.58		$898.5924	$898.59	$898.60	$898.50