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	$84.92	5.692%	$89.7536	$89.75	$89.75	$89.80
Purchase #2	$137.47	10.338%	$151.6816	$151.68	$151.70	$151.70
Purchase #3	$187.88	5.723%	$198.6324	$198.63	$198.65	$198.60
Purchase #4	$44.69	9.194%	$48.7988	$48.80	$48.80	$48.80
Purchase #5	$175.42	6.791%	$187.3328	$187.33	$187.35	$187.30
Purchase #6	$140.46	12.487%	$157.9992	$158.00	$158.00	$158.00
Purchase #7	$89.56	12.519%	$100.772	$100.77	$100.75	$100.80
7 purchase totals =	$860.40		$934.9704	$934.96	$935.00	$935.00