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	$165.60	3.498%	$171.3927	$171.39	$171.40	$171.40
Purchase #2	$237.52	13.443%	$269.4498	$269.45	$269.45	$269.40
Purchase #3	$47.88	7.666%	$51.5505	$51.55	$51.55	$51.60
Purchase #4	$59.82	10.724%	$66.2351	$66.24	$66.25	$66.20
Purchase #5	$203.51	8.473%	$220.7534	$220.75	$220.75	$220.80
Purchase #6	$105.38	10.566%	$116.5145	$116.51	$116.50	$116.50
Purchase #7	$110.85	7.271%	$118.9099	$118.91	$118.90	$118.90
7 purchase totals =	$930.56		$1,014.8059	$1,014.80	$1,014.80	$1,014.80