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	$196.79	9.446%	$215.3788	$215.38	$215.40	$215.40
Purchase #2	$30.60	4.643%	$32.0208	$32.02	$32.00	$32.00
Purchase #3	$117.40	13.174%	$132.8663	$132.87	$132.85	$132.90
Purchase #4	$171.50	10.538%	$189.5727	$189.57	$189.55	$189.60
Purchase #5	$77.34	6.609%	$82.4514	$82.45	$82.45	$82.50
Purchase #6	$249.57	9.637%	$273.6211	$273.62	$273.60	$273.60
Purchase #7	$138.96	11.114%	$154.404	$154.40	$154.40	$154.40
7 purchase totals =	$982.16		$1,080.3151	$1,080.31	$1,080.25	$1,080.40