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	$98.31	11.719%	$109.8309	$109.83	$109.85	$109.80
Purchase #2	$19.67	9.293%	$21.4979	$21.50	$21.50	$21.50
Purchase #3	$98.64	12.649%	$111.117	$111.12	$111.10	$111.10
Purchase #4	$196.85	12.826%	$222.098	$222.10	$222.10	$222.10
Purchase #5	$104.64	3.248%	$108.0387	$108.04	$108.05	$108.00
Purchase #6	$176.94	5.140%	$186.0347	$186.03	$186.05	$186.00
Purchase #7	$12.89	3.577%	$13.3511	$13.35	$13.35	$13.40
7 purchase totals =	$707.94		$771.9683	$771.97	$772.00	$771.90