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	$217.56	9.219%	$237.6169	$237.62	$237.60	$237.60
Purchase #2	$215.78	4.190%	$224.8212	$224.82	$224.80	$224.80
Purchase #3	$37.84	9.221%	$41.3292	$41.33	$41.35	$41.30
Purchase #4	$59.87	4.864%	$62.7821	$62.78	$62.80	$62.80
Purchase #5	$208.63	12.172%	$234.0244	$234.02	$234.00	$234.00
Purchase #6	$170.58	5.190%	$179.4331	$179.43	$179.45	$179.40
Purchase #7	$134.85	6.161%	$143.1581	$143.16	$143.15	$143.20
7 purchase totals =	$1,045.11		$1,123.1650	$1,123.16	$1,123.15	$1,123.10