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	$98.80	7.775%	$106.4817	$106.48	$106.50	$106.50
Purchase #2	$54.83	8.334%	$59.3995	$59.40	$59.40	$59.40
Purchase #3	$82.56	5.867%	$87.4038	$87.40	$87.40	$87.40
Purchase #4	$95.85	5.853%	$101.4601	$101.46	$101.45	$101.50
Purchase #5	$197.64	5.708%	$208.9213	$208.92	$208.90	$208.90
Purchase #6	$63.75	9.168%	$69.5946	$69.59	$69.60	$69.60
Purchase #7	$144.31	7.755%	$155.5012	$155.50	$155.50	$155.50
7 purchase totals =	$737.74		$788.7622	$788.75	$788.75	$788.80