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	$119.59	7.713%	$128.814	$128.81	$128.80	$128.80
Purchase #2	$243.82	5.196%	$256.4889	$256.49	$256.50	$256.50
Purchase #3	$172.75	7.700%	$186.0518	$186.05	$186.05	$186.10
Purchase #4	$183.27	3.538%	$189.7541	$189.75	$189.75	$189.80
Purchase #5	$172.85	11.576%	$192.8591	$192.86	$192.85	$192.90
Purchase #6	$93.45	12.763%	$105.377	$105.38	$105.40	$105.40
Purchase #7	$113.61	6.778%	$121.3105	$121.31	$121.30	$121.30
7 purchase totals =	$1,099.34		$1,180.6554	$1,180.65	$1,180.65	$1,180.80