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	$108.33	3.725%	$112.3653	$112.37	$112.35	$112.40
Purchase #2	$130.87	13.437%	$148.455	$148.46	$148.45	$148.50
Purchase #3	$86.50	4.543%	$90.4297	$90.43	$90.45	$90.40
Purchase #4	$240.99	8.552%	$261.5995	$261.60	$261.60	$261.60
Purchase #5	$30.44	12.672%	$34.2974	$34.30	$34.30	$34.30
Purchase #6	$189.96	8.684%	$206.4561	$206.46	$206.45	$206.50
Purchase #7	$220.53	5.130%	$231.8432	$231.84	$231.85	$231.80
7 purchase totals =	$1,007.62		$1,085.4462	$1,085.46	$1,085.45	$1,085.50