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	$217.77	9.217%	$237.8419	$237.84	$237.85	$237.80
Purchase #2	$59.38	13.759%	$67.5501	$67.55	$67.55	$67.60
Purchase #3	$204.45	5.308%	$215.3022	$215.30	$215.30	$215.30
Purchase #4	$45.88	4.748%	$48.0584	$48.06	$48.05	$48.10
Purchase #5	$208.69	13.217%	$236.2726	$236.27	$236.25	$236.30
Purchase #6	$150.57	5.165%	$158.3469	$158.35	$158.35	$158.30
Purchase #7	$121.35	12.471%	$136.4836	$136.48	$136.50	$136.50
7 purchase totals =	$1,008.09		$1,099.8557	$1,099.85	$1,099.85	$1,099.90