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	$81.29	11.584%	$90.7066	$90.71	$90.70	$90.70
Purchase #2	$94.64	5.293%	$99.6493	$99.65	$99.65	$99.60
Purchase #3	$37.65	8.778%	$40.9549	$40.95	$40.95	$41.00
Purchase #4	$122.99	9.257%	$134.3752	$134.38	$134.40	$134.40
Purchase #5	$150.89	12.191%	$169.285	$169.29	$169.30	$169.30
Purchase #6	$142.51	8.343%	$154.3996	$154.40	$154.40	$154.40
Purchase #7	$239.45	6.871%	$255.9026	$255.90	$255.90	$255.90
7 purchase totals =	$869.42		$945.2732	$945.28	$945.30	$945.30