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	$82.75	13.751%	$94.129	$94.13	$94.15	$94.10
Purchase #2	$183.38	4.619%	$191.8503	$191.85	$191.85	$191.90
Purchase #3	$37.45	12.166%	$42.0062	$42.01	$42.00	$42.00
Purchase #4	$102.67	6.423%	$109.2645	$109.26	$109.25	$109.30
Purchase #5	$239.44	13.571%	$271.9344	$271.93	$271.95	$271.90
Purchase #6	$121.56	12.575%	$136.8462	$136.85	$136.85	$136.80
Purchase #7	$77.44	13.476%	$87.8758	$87.88	$87.90	$87.90
7 purchase totals =	$844.69		$933.9064	$933.91	$933.95	$933.90