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	$60.70	3.332%	$62.7225	$62.72	$62.70	$62.70
Purchase #2	$37.74	6.435%	$40.1686	$40.17	$40.15	$40.20
Purchase #3	$250.46	4.834%	$262.5672	$262.57	$262.55	$262.60
Purchase #4	$143.74	9.129%	$156.862	$156.86	$156.85	$156.90
Purchase #5	$77.88	7.169%	$83.4632	$83.46	$83.45	$83.50
Purchase #6	$168.46	11.448%	$187.7453	$187.75	$187.75	$187.70
Purchase #7	$234.25	7.648%	$252.1654	$252.17	$252.15	$252.20
7 purchase totals =	$973.23		$1,045.6942	$1,045.70	$1,045.60	$1,045.80