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	$84.95	12.470%	$95.5433	$95.54	$95.55	$95.50
Purchase #2	$115.37	3.712%	$119.6525	$119.65	$119.65	$119.70
Purchase #3	$80.85	3.566%	$83.7331	$83.73	$83.75	$83.70
Purchase #4	$13.68	13.474%	$15.5232	$15.52	$15.50	$15.50
Purchase #5	$83.41	13.468%	$94.6437	$94.64	$94.65	$94.60
Purchase #6	$120.67	4.798%	$126.4597	$126.46	$126.45	$126.50
Purchase #7	$122.42	7.263%	$131.3114	$131.31	$131.30	$131.30
7 purchase totals =	$621.35		$666.8669	$666.85	$666.85	$666.80