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	$63.41	6.262%	$67.3807	$67.38	$67.40	$67.40
Purchase #2	$36.40	7.585%	$39.1609	$39.16	$39.15	$39.20
Purchase #3	$106.97	9.109%	$116.7139	$116.71	$116.70	$116.70
Purchase #4	$169.89	13.657%	$193.0919	$193.09	$193.10	$193.10
Purchase #5	$212.67	7.268%	$228.1269	$228.13	$228.15	$228.10
Purchase #6	$167.46	11.335%	$186.4416	$186.44	$186.45	$186.40
Purchase #7	$164.52	12.806%	$185.5884	$185.59	$185.60	$185.60
7 purchase totals =	$921.32		$1,016.5043	$1,016.50	$1,016.55	$1,016.50