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	$32.61	12.207%	$36.5907	$36.59	$36.60	$36.60
Purchase #2	$237.57	13.615%	$269.9152	$269.92	$269.90	$269.90
Purchase #3	$152.93	8.853%	$166.4689	$166.47	$166.45	$166.50
Purchase #4	$246.83	5.505%	$260.418	$260.42	$260.40	$260.40
Purchase #5	$34.38	9.574%	$37.6715	$37.67	$37.65	$37.70
Purchase #6	$155.57	4.167%	$162.0526	$162.05	$162.05	$162.10
Purchase #7	$236.47	8.397%	$256.3264	$256.33	$256.35	$256.30
7 purchase totals =	$1,096.36		$1,189.4433	$1,189.45	$1,189.40	$1,189.50