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	$207.73	6.816%	$221.8889	$221.89	$221.90	$221.90
Purchase #2	$102.83	13.383%	$116.5917	$116.59	$116.60	$116.60
Purchase #3	$241.46	12.475%	$271.5821	$271.58	$271.60	$271.60
Purchase #4	$81.31	12.868%	$91.773	$91.77	$91.75	$91.80
Purchase #5	$223.47	5.841%	$236.5229	$236.52	$236.50	$236.50
Purchase #6	$62.86	12.259%	$70.566	$70.57	$70.55	$70.60
Purchase #7	$58.67	13.529%	$66.6075	$66.61	$66.60	$66.60
7 purchase totals =	$978.33		$1,075.5321	$1,075.53	$1,075.50	$1,075.60