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	$113.40	11.242%	$126.1484	$126.15	$126.15	$126.10
Purchase #2	$91.32	12.767%	$102.9788	$102.98	$103.00	$103.00
Purchase #3	$40.31	3.142%	$41.5765	$41.58	$41.60	$41.60
Purchase #4	$154.66	13.587%	$175.6737	$175.67	$175.65	$175.70
Purchase #5	$72.43	8.438%	$78.5416	$78.54	$78.55	$78.50
Purchase #6	$70.72	13.158%	$80.0253	$80.03	$80.05	$80.00
Purchase #7	$81.90	6.742%	$87.4217	$87.42	$87.40	$87.40
7 purchase totals =	$624.74		$692.3660	$692.37	$692.40	$692.30