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	$228.91	5.563%	$241.6443	$241.64	$241.65	$241.60
Purchase #2	$208.43	6.273%	$221.5048	$221.50	$221.50	$221.50
Purchase #3	$130.39	9.553%	$142.8462	$142.85	$142.85	$142.80
Purchase #4	$169.81	11.491%	$189.3229	$189.32	$189.30	$189.30
Purchase #5	$33.55	13.102%	$37.9457	$37.95	$37.95	$37.90
Purchase #6	$188.41	5.671%	$199.0947	$199.09	$199.10	$199.10
Purchase #7	$58.66	12.664%	$66.0887	$66.09	$66.10	$66.10
7 purchase totals =	$1,018.16		$1,098.4473	$1,098.44	$1,098.45	$1,098.30