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	$12.28	13.470%	$13.9341	$13.93	$13.95	$13.90
Purchase #2	$89.85	4.732%	$94.1017	$94.10	$94.10	$94.10
Purchase #3	$92.96	3.177%	$95.9133	$95.91	$95.90	$95.90
Purchase #4	$241.73	7.718%	$260.3867	$260.39	$260.40	$260.40
Purchase #5	$151.32	11.364%	$168.516	$168.52	$168.50	$168.50
Purchase #6	$112.89	5.632%	$119.248	$119.25	$119.25	$119.20
Purchase #7	$171.59	4.806%	$179.8366	$179.84	$179.85	$179.80
7 purchase totals =	$872.62		$931.9364	$931.94	$931.95	$931.80