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	$105.81	3.641%	$109.6625	$109.66	$109.65	$109.70
Purchase #2	$133.87	12.274%	$150.3012	$150.30	$150.30	$150.30
Purchase #3	$123.45	10.770%	$136.7456	$136.75	$136.75	$136.70
Purchase #4	$241.53	6.545%	$257.3381	$257.34	$257.35	$257.30
Purchase #5	$49.33	10.293%	$54.4075	$54.41	$54.40	$54.40
Purchase #6	$99.71	12.203%	$111.8776	$111.88	$111.90	$111.90
Purchase #7	$185.77	4.125%	$193.433	$193.43	$193.45	$193.40
7 purchase totals =	$939.47		$1,013.7655	$1,013.77	$1,013.80	$1,013.70