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	$245.52	8.724%	$266.9392	$266.94	$266.95	$266.90
Purchase #2	$31.61	9.437%	$34.593	$34.59	$34.60	$34.60
Purchase #3	$130.55	5.310%	$137.4822	$137.48	$137.50	$137.50
Purchase #4	$113.63	11.201%	$126.3577	$126.36	$126.35	$126.40
Purchase #5	$137.59	10.321%	$151.7907	$151.79	$151.80	$151.80
Purchase #6	$123.86	10.180%	$136.4689	$136.47	$136.45	$136.50
Purchase #7	$203.42	9.532%	$222.81	$222.81	$222.80	$222.80
7 purchase totals =	$986.18		$1,076.4417	$1,076.44	$1,076.45	$1,076.50