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	$231.93	7.624%	$249.6123	$249.61	$249.60	$249.60
Purchase #2	$208.60	6.784%	$222.7514	$222.75	$222.75	$222.80
Purchase #3	$51.65	6.227%	$54.8662	$54.87	$54.85	$54.90
Purchase #4	$202.51	9.614%	$221.9793	$221.98	$222.00	$222.00
Purchase #5	$183.30	12.280%	$205.8092	$205.81	$205.80	$205.80
Purchase #6	$83.68	7.845%	$90.2447	$90.24	$90.25	$90.20
Purchase #7	$198.93	8.202%	$215.2462	$215.25	$215.25	$215.20
7 purchase totals =	$1,160.60		$1,260.5093	$1,260.51	$1,260.50	$1,260.50