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	$85.37	10.807%	$94.5959	$94.60	$94.60	$94.60
Purchase #2	$135.76	4.171%	$141.4225	$141.42	$141.40	$141.40
Purchase #3	$46.52	10.250%	$51.2883	$51.29	$51.30	$51.30
Purchase #4	$41.49	4.280%	$43.2658	$43.27	$43.25	$43.30
Purchase #5	$39.56	9.509%	$43.3218	$43.32	$43.30	$43.30
Purchase #6	$183.35	7.783%	$197.6201	$197.62	$197.60	$197.60
Purchase #7	$76.33	12.391%	$85.7881	$85.79	$85.80	$85.80
7 purchase totals =	$608.38		$657.3025	$657.31	$657.25	$657.30