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	$100.63	4.780%	$105.4401	$105.44	$105.45	$105.40
Purchase #2	$40.75	7.866%	$43.9554	$43.96	$43.95	$44.00
Purchase #3	$30.34	10.443%	$33.5084	$33.51	$33.50	$33.50
Purchase #4	$242.56	12.683%	$273.3239	$273.32	$273.30	$273.30
Purchase #5	$62.94	5.870%	$66.6346	$66.63	$66.65	$66.60
Purchase #6	$8.42	4.525%	$8.801	$8.80	$8.80	$8.80
Purchase #7	$92.55	8.123%	$100.0678	$100.07	$100.05	$100.10
7 purchase totals =	$578.19		$631.7312	$631.73	$631.70	$631.70