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	$36.77	13.390%	$41.6935	$41.69	$41.70	$41.70
Purchase #2	$190.51	13.816%	$216.8309	$216.83	$216.85	$216.80
Purchase #3	$120.86	4.612%	$126.4341	$126.43	$126.45	$126.40
Purchase #4	$238.54	13.105%	$269.8007	$269.80	$269.80	$269.80
Purchase #5	$219.82	12.639%	$247.603	$247.60	$247.60	$247.60
Purchase #6	$248.38	10.368%	$274.132	$274.13	$274.15	$274.10
Purchase #7	$248.86	4.407%	$259.8273	$259.83	$259.85	$259.80
7 purchase totals =	$1,303.74		$1,436.3215	$1,436.31	$1,436.40	$1,436.20