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	$137.83	11.446%	$153.606	$153.61	$153.60	$153.60
Purchase #2	$160.56	5.283%	$169.0424	$169.04	$169.05	$169.00
Purchase #3	$99.45	13.200%	$112.5774	$112.58	$112.60	$112.60
Purchase #4	$167.34	10.467%	$184.8555	$184.86	$184.85	$184.90
Purchase #5	$160.50	13.273%	$181.8032	$181.80	$181.80	$181.80
Purchase #6	$237.38	11.792%	$265.3718	$265.37	$265.35	$265.40
Purchase #7	$12.32	9.653%	$13.5092	$13.51	$13.50	$13.50
7 purchase totals =	$975.38		$1,080.7655	$1,080.77	$1,080.75	$1,080.80