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	$236.37	6.870%	$252.6086	$252.61	$252.60	$252.60
Purchase #2	$198.86	5.739%	$210.2726	$210.27	$210.25	$210.30
Purchase #3	$53.51	11.681%	$59.7605	$59.76	$59.75	$59.80
Purchase #4	$50.55	8.820%	$55.0085	$55.01	$55.00	$55.00
Purchase #5	$40.68	6.830%	$43.4584	$43.46	$43.45	$43.50
Purchase #6	$20.69	12.866%	$23.352	$23.35	$23.35	$23.40
Purchase #7	$104.81	10.181%	$115.4807	$115.48	$115.50	$115.50
7 purchase totals =	$705.47		$759.9413	$759.94	$759.90	$760.10