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	$245.77	11.803%	$274.7782	$274.78	$274.80	$274.80
Purchase #2	$120.35	11.229%	$133.8641	$133.86	$133.85	$133.90
Purchase #3	$73.30	11.418%	$81.6694	$81.67	$81.65	$81.70
Purchase #4	$231.80	12.414%	$260.5757	$260.58	$260.60	$260.60
Purchase #5	$45.83	5.826%	$48.5001	$48.50	$48.50	$48.50
Purchase #6	$196.52	11.743%	$219.5973	$219.60	$219.60	$219.60
Purchase #7	$140.37	4.348%	$146.4733	$146.47	$146.45	$146.50
7 purchase totals =	$1,053.94		$1,165.4581	$1,165.46	$1,165.45	$1,165.60