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	$95.38	5.143%	$100.2854	$100.29	$100.30	$100.30
Purchase #2	$111.72	5.343%	$117.6892	$117.69	$117.70	$117.70
Purchase #3	$186.56	10.149%	$205.494	$205.49	$205.50	$205.50
Purchase #4	$17.66	9.348%	$19.3109	$19.31	$19.30	$19.30
Purchase #5	$160.33	3.193%	$165.4493	$165.45	$165.45	$165.40
Purchase #6	$181.61	13.473%	$206.0783	$206.08	$206.10	$206.10
Purchase #7	$80.89	13.261%	$91.6168	$91.62	$91.60	$91.60
7 purchase totals =	$834.15		$905.9239	$905.93	$905.95	$905.90