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	$60.54	11.628%	$67.5796	$67.58	$67.60	$67.60
Purchase #2	$62.53	12.593%	$70.4044	$70.40	$70.40	$70.40
Purchase #3	$50.85	7.121%	$54.471	$54.47	$54.45	$54.50
Purchase #4	$86.44	9.329%	$94.504	$94.50	$94.50	$94.50
Purchase #5	$217.57	3.147%	$224.4169	$224.42	$224.40	$224.40
Purchase #6	$137.58	5.813%	$145.5775	$145.58	$145.60	$145.60
Purchase #7	$78.33	8.678%	$85.1275	$85.13	$85.15	$85.10
7 purchase totals =	$693.84		$742.0809	$742.08	$742.10	$742.10