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	$89.50	9.596%	$98.0884	$98.09	$98.10	$98.10
Purchase #2	$132.59	7.755%	$142.8724	$142.87	$142.85	$142.90
Purchase #3	$173.32	6.163%	$184.0017	$184.00	$184.00	$184.00
Purchase #4	$160.33	13.549%	$182.0531	$182.05	$182.05	$182.10
Purchase #5	$226.94	6.544%	$241.791	$241.79	$241.80	$241.80
Purchase #6	$128.83	10.431%	$142.2683	$142.27	$142.25	$142.30
Purchase #7	$27.87	13.434%	$31.6141	$31.61	$31.60	$31.60
7 purchase totals =	$939.38		$1,022.6890	$1,022.68	$1,022.65	$1,022.80