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	$54.66	5.107%	$57.4515	$57.45	$57.45	$57.50
Purchase #2	$241.93	11.706%	$270.2503	$270.25	$270.25	$270.30
Purchase #3	$76.82	11.273%	$85.4799	$85.48	$85.50	$85.50
Purchase #4	$201.89	10.667%	$223.4256	$223.43	$223.45	$223.40
Purchase #5	$139.77	6.326%	$148.6119	$148.61	$148.60	$148.60
Purchase #6	$205.46	10.771%	$227.5901	$227.59	$227.60	$227.60
Purchase #7	$57.66	9.764%	$63.2899	$63.29	$63.30	$63.30
7 purchase totals =	$978.19		$1,076.0992	$1,076.10	$1,076.15	$1,076.20