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	$79.72	6.737%	$85.0907	$85.09	$85.10	$85.10
Purchase #2	$107.56	8.834%	$117.0619	$117.06	$117.05	$117.10
Purchase #3	$42.94	9.201%	$46.8909	$46.89	$46.90	$46.90
Purchase #4	$99.72	13.607%	$113.2889	$113.29	$113.30	$113.30
Purchase #5	$196.39	13.166%	$222.2467	$222.25	$222.25	$222.20
Purchase #6	$193.60	10.430%	$213.7925	$213.79	$213.80	$213.80
Purchase #7	$158.92	4.206%	$165.6042	$165.60	$165.60	$165.60
7 purchase totals =	$878.85		$963.9758	$963.97	$964.00	$964.00