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	$67.68	5.314%	$71.2765	$71.28	$71.30	$71.30
Purchase #2	$103.88	10.634%	$114.9266	$114.93	$114.95	$114.90
Purchase #3	$11.88	10.622%	$13.1419	$13.14	$13.15	$13.10
Purchase #4	$92.92	7.615%	$99.9959	$100.00	$100.00	$100.00
Purchase #5	$112.73	11.672%	$125.8878	$125.89	$125.90	$125.90
Purchase #6	$42.29	7.623%	$45.5138	$45.51	$45.50	$45.50
Purchase #7	$201.25	7.832%	$217.0119	$217.01	$217.00	$217.00
7 purchase totals =	$632.63		$687.7544	$687.76	$687.80	$687.70