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	$75.46	9.185%	$82.391	$82.39	$82.40	$82.40
Purchase #2	$121.93	9.525%	$133.5438	$133.54	$133.55	$133.50
Purchase #3	$169.38	9.184%	$184.9359	$184.94	$184.95	$184.90
Purchase #4	$103.82	4.260%	$108.2427	$108.24	$108.25	$108.20
Purchase #5	$206.81	3.616%	$214.2882	$214.29	$214.30	$214.30
Purchase #6	$84.98	6.179%	$90.2309	$90.23	$90.25	$90.20
Purchase #7	$140.50	4.117%	$146.2844	$146.28	$146.30	$146.30
7 purchase totals =	$902.88		$959.9169	$959.91	$960.00	$959.80