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	$241.54	9.500%	$264.4863	$264.49	$264.50	$264.50
Purchase #2	$37.25	11.185%	$41.4164	$41.42	$41.40	$41.40
Purchase #3	$105.74	5.393%	$111.4426	$111.44	$111.45	$111.40
Purchase #4	$35.93	12.668%	$40.4816	$40.48	$40.50	$40.50
Purchase #5	$99.57	12.141%	$111.6588	$111.66	$111.65	$111.70
Purchase #6	$32.74	4.136%	$34.0941	$34.09	$34.10	$34.10
Purchase #7	$52.55	7.170%	$56.3178	$56.32	$56.30	$56.30
7 purchase totals =	$605.32		$659.8976	$659.90	$659.90	$659.90