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	$37.84	9.758%	$41.5324	$41.53	$41.55	$41.50
Purchase #2	$67.70	13.517%	$76.851	$76.85	$76.85	$76.90
Purchase #3	$87.87	7.419%	$94.3891	$94.39	$94.40	$94.40
Purchase #4	$117.69	7.179%	$126.139	$126.14	$126.15	$126.10
Purchase #5	$34.66	8.543%	$37.621	$37.62	$37.60	$37.60
Purchase #6	$76.64	7.659%	$82.5099	$82.51	$82.50	$82.50
Purchase #7	$144.92	10.528%	$160.1772	$160.18	$160.20	$160.20
7 purchase totals =	$567.32		$619.2196	$619.22	$619.25	$619.20