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	$213.52	7.725%	$230.0144	$230.01	$230.00	$230.00
Purchase #2	$27.39	5.258%	$28.8302	$28.83	$28.85	$28.80
Purchase #3	$239.80	5.539%	$253.0825	$253.08	$253.10	$253.10
Purchase #4	$63.78	6.451%	$67.8944	$67.89	$67.90	$67.90
Purchase #5	$105.74	4.483%	$110.4803	$110.48	$110.50	$110.50
Purchase #6	$78.96	13.611%	$89.7072	$89.71	$89.70	$89.70
Purchase #7	$158.26	13.393%	$179.4558	$179.46	$179.45	$179.50
7 purchase totals =	$887.45		$959.4648	$959.46	$959.50	$959.50