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	$101.34	10.666%	$112.1489	$112.15	$112.15	$112.10
Purchase #2	$117.56	8.418%	$127.4562	$127.46	$127.45	$127.50
Purchase #3	$206.85	5.302%	$217.8172	$217.82	$217.80	$217.80
Purchase #4	$66.35	7.156%	$71.098	$71.10	$71.10	$71.10
Purchase #5	$158.92	13.773%	$180.8081	$180.81	$180.80	$180.80
Purchase #6	$166.58	4.418%	$173.9395	$173.94	$173.95	$173.90
Purchase #7	$198.70	10.483%	$219.5297	$219.53	$219.55	$219.50
7 purchase totals =	$1,016.30		$1,102.7976	$1,102.81	$1,102.80	$1,102.70