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	$43.81	8.357%	$47.4712	$47.47	$47.45	$47.50
Purchase #2	$97.53	8.258%	$105.584	$105.58	$105.60	$105.60
Purchase #3	$236.51	11.137%	$262.8501	$262.85	$262.85	$262.90
Purchase #4	$125.25	5.367%	$131.9722	$131.97	$131.95	$132.00
Purchase #5	$149.58	6.802%	$159.7544	$159.75	$159.75	$159.80
Purchase #6	$134.82	3.514%	$139.5576	$139.56	$139.55	$139.60
Purchase #7	$192.84	12.326%	$216.6095	$216.61	$216.60	$216.60
7 purchase totals =	$980.34		$1,063.7990	$1,063.79	$1,063.75	$1,064.00