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	$95.50	4.348%	$99.6523	$99.65	$99.65	$99.70
Purchase #2	$223.51	11.771%	$249.8194	$249.82	$249.80	$249.80
Purchase #3	$126.67	4.537%	$132.417	$132.42	$132.40	$132.40
Purchase #4	$44.43	12.656%	$50.0531	$50.05	$50.05	$50.10
Purchase #5	$120.32	10.423%	$132.861	$132.86	$132.85	$132.90
Purchase #6	$103.86	10.210%	$114.4641	$114.46	$114.45	$114.50
Purchase #7	$153.55	8.311%	$166.3115	$166.31	$166.30	$166.30
7 purchase totals =	$867.84		$945.5784	$945.57	$945.50	$945.70