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	$233.98	11.494%	$260.8737	$260.87	$260.85	$260.90
Purchase #2	$165.50	11.812%	$185.0489	$185.05	$185.05	$185.00
Purchase #3	$128.60	3.348%	$132.9055	$132.91	$132.90	$132.90
Purchase #4	$216.43	5.286%	$227.8705	$227.87	$227.85	$227.90
Purchase #5	$222.38	8.189%	$240.5907	$240.59	$240.60	$240.60
Purchase #6	$146.81	8.183%	$158.8235	$158.82	$158.80	$158.80
Purchase #7	$33.50	3.317%	$34.6112	$34.61	$34.60	$34.60
7 purchase totals =	$1,147.20		$1,240.7240	$1,240.72	$1,240.65	$1,240.70