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	$204.76	10.834%	$226.9437	$226.94	$226.95	$226.90
Purchase #2	$18.37	11.161%	$20.4203	$20.42	$20.40	$20.40
Purchase #3	$175.81	6.454%	$187.1568	$187.16	$187.15	$187.20
Purchase #4	$136.52	4.560%	$142.7453	$142.75	$142.75	$142.70
Purchase #5	$117.87	4.745%	$123.4629	$123.46	$123.45	$123.50
Purchase #6	$33.86	13.638%	$38.4778	$38.48	$38.50	$38.50
Purchase #7	$109.62	13.358%	$124.263	$124.26	$124.25	$124.30
7 purchase totals =	$796.81		$863.4698	$863.47	$863.45	$863.50