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	$38.86	11.799%	$43.4451	$43.45	$43.45	$43.40
Purchase #2	$224.82	10.685%	$248.842	$248.84	$248.85	$248.80
Purchase #3	$155.85	11.328%	$173.5047	$173.50	$173.50	$173.50
Purchase #4	$91.56	4.798%	$95.953	$95.95	$95.95	$96.00
Purchase #5	$30.82	11.706%	$34.4278	$34.43	$34.45	$34.40
Purchase #6	$242.25	11.514%	$270.1427	$270.14	$270.15	$270.10
Purchase #7	$13.54	4.471%	$14.1454	$14.15	$14.15	$14.10
7 purchase totals =	$797.70		$880.4607	$880.46	$880.50	$880.30