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	$109.57	10.576%	$121.1581	$121.16	$121.15	$121.20
Purchase #2	$49.94	11.123%	$55.4948	$55.49	$55.50	$55.50
Purchase #3	$235.71	8.667%	$256.139	$256.14	$256.15	$256.10
Purchase #4	$123.27	3.613%	$127.7237	$127.72	$127.70	$127.70
Purchase #5	$169.81	12.360%	$190.7985	$190.80	$190.80	$190.80
Purchase #6	$217.69	3.474%	$225.2526	$225.25	$225.25	$225.30
Purchase #7	$113.45	5.105%	$119.2416	$119.24	$119.25	$119.20
7 purchase totals =	$1,019.44		$1,095.8083	$1,095.80	$1,095.80	$1,095.80