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	$110.64	3.791%	$114.8344	$114.83	$114.85	$114.80
Purchase #2	$243.92	13.751%	$277.4614	$277.46	$277.45	$277.50
Purchase #3	$188.25	10.757%	$208.5001	$208.50	$208.50	$208.50
Purchase #4	$200.30	8.310%	$216.9449	$216.94	$216.95	$216.90
Purchase #5	$228.40	11.143%	$253.8506	$253.85	$253.85	$253.90
Purchase #6	$242.26	11.371%	$269.8074	$269.81	$269.80	$269.80
Purchase #7	$187.91	6.677%	$200.4568	$200.46	$200.45	$200.50
7 purchase totals =	$1,401.68		$1,541.8556	$1,541.85	$1,541.85	$1,541.90