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	$29.42	13.726%	$33.4582	$33.46	$33.45	$33.50
Purchase #2	$95.47	9.668%	$104.7	$104.70	$104.70	$104.70
Purchase #3	$189.38	10.332%	$208.9467	$208.95	$208.95	$208.90
Purchase #4	$172.61	8.702%	$187.6305	$187.63	$187.65	$187.60
Purchase #5	$161.53	8.665%	$175.5266	$175.53	$175.55	$175.50
Purchase #6	$242.39	9.326%	$264.9953	$265.00	$265.00	$265.00
Purchase #7	$157.32	11.565%	$175.5141	$175.51	$175.50	$175.50
7 purchase totals =	$1,048.12		$1,150.7714	$1,150.78	$1,150.80	$1,150.70