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	$209.27	4.141%	$217.9359	$217.94	$217.95	$217.90
Purchase #2	$237.37	13.686%	$269.8565	$269.86	$269.85	$269.90
Purchase #3	$33.82	6.724%	$36.0941	$36.09	$36.10	$36.10
Purchase #4	$12.73	10.797%	$14.1045	$14.10	$14.10	$14.10
Purchase #5	$136.85	10.114%	$150.691	$150.69	$150.70	$150.70
Purchase #6	$119.62	6.724%	$127.6632	$127.66	$127.65	$127.70
Purchase #7	$74.58	10.477%	$82.3937	$82.39	$82.40	$82.40
7 purchase totals =	$824.24		$898.7389	$898.73	$898.75	$898.80