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	$168.39	3.666%	$174.5632	$174.56	$174.55	$174.60
Purchase #2	$133.90	7.114%	$143.4256	$143.43	$143.45	$143.40
Purchase #3	$126.65	13.429%	$143.6578	$143.66	$143.65	$143.70
Purchase #4	$46.29	7.278%	$49.659	$49.66	$49.65	$49.70
Purchase #5	$112.55	12.679%	$126.8202	$126.82	$126.80	$126.80
Purchase #6	$164.87	12.528%	$185.5249	$185.52	$185.50	$185.50
Purchase #7	$28.32	9.712%	$31.0704	$31.07	$31.05	$31.10
7 purchase totals =	$780.97		$854.7211	$854.72	$854.65	$854.80