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	$126.85	4.437%	$132.4783	$132.48	$132.50	$132.50
Purchase #2	$177.87	10.676%	$196.8594	$196.86	$196.85	$196.90
Purchase #3	$132.79	11.309%	$147.8072	$147.81	$147.80	$147.80
Purchase #4	$204.89	10.458%	$226.3174	$226.32	$226.30	$226.30
Purchase #5	$92.73	13.112%	$104.8888	$104.89	$104.90	$104.90
Purchase #6	$15.60	5.713%	$16.4912	$16.49	$16.50	$16.50
Purchase #7	$85.72	9.654%	$93.9954	$94.00	$94.00	$94.00
7 purchase totals =	$836.45		$918.8377	$918.85	$918.85	$918.90