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	$227.38	5.374%	$239.5994	$239.60	$239.60	$239.60
Purchase #2	$131.86	12.448%	$148.2739	$148.27	$148.25	$148.30
Purchase #3	$246.84	5.838%	$261.2505	$261.25	$261.25	$261.30
Purchase #4	$106.61	4.819%	$111.7475	$111.75	$111.75	$111.70
Purchase #5	$111.54	10.421%	$123.1636	$123.16	$123.15	$123.20
Purchase #6	$22.64	3.623%	$23.4602	$23.46	$23.45	$23.50
Purchase #7	$111.36	6.255%	$118.3256	$118.33	$118.35	$118.30
7 purchase totals =	$958.23		$1,025.8207	$1,025.82	$1,025.80	$1,025.90