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	$87.62	7.704%	$94.3702	$94.37	$94.35	$94.40
Purchase #2	$78.50	8.709%	$85.3366	$85.34	$85.35	$85.30
Purchase #3	$242.61	10.651%	$268.4504	$268.45	$268.45	$268.50
Purchase #4	$241.41	8.716%	$262.4513	$262.45	$262.45	$262.50
Purchase #5	$163.43	6.576%	$174.1772	$174.18	$174.20	$174.20
Purchase #6	$231.82	12.493%	$260.7813	$260.78	$260.80	$260.80
Purchase #7	$139.39	9.636%	$152.8216	$152.82	$152.80	$152.80
7 purchase totals =	$1,184.78		$1,298.3886	$1,298.39	$1,298.40	$1,298.50