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	$200.83	8.297%	$217.4929	$217.49	$217.50	$217.50
Purchase #2	$239.64	9.529%	$262.4753	$262.48	$262.50	$262.50
Purchase #3	$10.41	4.154%	$10.8424	$10.84	$10.85	$10.80
Purchase #4	$154.44	12.791%	$174.1944	$174.19	$174.20	$174.20
Purchase #5	$121.81	8.212%	$131.813	$131.81	$131.80	$131.80
Purchase #6	$144.47	5.547%	$152.4838	$152.48	$152.50	$152.50
Purchase #7	$123.31	3.413%	$127.5186	$127.52	$127.50	$127.50
7 purchase totals =	$994.91		$1,076.8204	$1,076.81	$1,076.85	$1,076.80