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	$98.73	11.252%	$109.8391	$109.84	$109.85	$109.80
Purchase #2	$66.65	5.225%	$70.1325	$70.13	$70.15	$70.10
Purchase #3	$203.70	13.525%	$231.2504	$231.25	$231.25	$231.30
Purchase #4	$238.32	11.181%	$264.9666	$264.97	$264.95	$265.00
Purchase #5	$128.83	5.619%	$136.069	$136.07	$136.05	$136.10
Purchase #6	$127.28	9.680%	$139.6007	$139.60	$139.60	$139.60
Purchase #7	$95.52	7.287%	$102.4805	$102.48	$102.50	$102.50
7 purchase totals =	$959.03		$1,054.3388	$1,054.34	$1,054.35	$1,054.40