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	$212.69	4.598%	$222.4695	$222.47	$222.45	$222.50
Purchase #2	$42.38	9.871%	$46.5633	$46.56	$46.55	$46.60
Purchase #3	$154.38	10.721%	$170.9311	$170.93	$170.95	$170.90
Purchase #4	$207.75	11.678%	$232.011	$232.01	$232.00	$232.00
Purchase #5	$154.63	11.611%	$172.5841	$172.58	$172.60	$172.60
Purchase #6	$230.98	12.798%	$260.5408	$260.54	$260.55	$260.50
Purchase #7	$70.61	3.188%	$72.861	$72.86	$72.85	$72.90
7 purchase totals =	$1,073.42		$1,177.9608	$1,177.95	$1,177.95	$1,178.00