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	$72.29	8.595%	$78.5033	$78.50	$78.50	$78.50
Purchase #2	$107.32	5.554%	$113.2806	$113.28	$113.30	$113.30
Purchase #3	$116.82	7.798%	$125.9296	$125.93	$125.95	$125.90
Purchase #4	$189.30	5.401%	$199.5241	$199.52	$199.50	$199.50
Purchase #5	$232.68	3.746%	$241.3962	$241.40	$241.40	$241.40
Purchase #6	$126.61	11.223%	$140.8194	$140.82	$140.80	$140.80
Purchase #7	$180.82	3.343%	$186.8648	$186.86	$186.85	$186.90
7 purchase totals =	$1,025.84		$1,086.3180	$1,086.31	$1,086.30	$1,086.30