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	$234.62	12.634%	$264.2619	$264.26	$264.25	$264.30
Purchase #2	$118.57	6.735%	$126.5557	$126.56	$126.55	$126.60
Purchase #3	$182.60	9.458%	$199.8703	$199.87	$199.85	$199.90
Purchase #4	$29.45	5.564%	$31.0886	$31.09	$31.10	$31.10
Purchase #5	$100.49	5.268%	$105.7838	$105.78	$105.80	$105.80
Purchase #6	$127.59	7.604%	$137.2919	$137.29	$137.30	$137.30
Purchase #7	$61.61	11.197%	$68.5085	$68.51	$68.50	$68.50
7 purchase totals =	$854.93		$933.3607	$933.36	$933.35	$933.50