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	$46.56	4.307%	$48.5653	$48.57	$48.55	$48.60
Purchase #2	$38.31	11.520%	$42.7233	$42.72	$42.70	$42.70
Purchase #3	$113.25	3.181%	$116.8525	$116.85	$116.85	$116.90
Purchase #4	$30.65	3.178%	$31.6241	$31.62	$31.60	$31.60
Purchase #5	$214.32	6.365%	$227.9615	$227.96	$227.95	$228.00
Purchase #6	$144.51	12.450%	$162.5015	$162.50	$162.50	$162.50
Purchase #7	$33.92	4.769%	$35.5376	$35.54	$35.55	$35.50
7 purchase totals =	$621.52		$665.7658	$665.76	$665.70	$665.80