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	$161.56	7.420%	$173.5478	$173.55	$173.55	$173.50
Purchase #2	$85.63	10.378%	$94.5167	$94.52	$94.50	$94.50
Purchase #3	$180.50	3.873%	$187.4908	$187.49	$187.50	$187.50
Purchase #4	$198.72	12.158%	$222.8804	$222.88	$222.90	$222.90
Purchase #5	$12.46	7.164%	$13.3526	$13.35	$13.35	$13.40
Purchase #6	$67.63	13.622%	$76.8426	$76.84	$76.85	$76.80
Purchase #7	$57.41	4.273%	$59.8631	$59.86	$59.85	$59.90
7 purchase totals =	$763.91		$828.4940	$828.49	$828.50	$828.50