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	$94.65	7.483%	$101.7327	$101.73	$101.75	$101.70
Purchase #2	$30.77	11.711%	$34.3735	$34.37	$34.35	$34.40
Purchase #3	$192.77	6.768%	$205.8167	$205.82	$205.80	$205.80
Purchase #4	$217.45	6.557%	$231.7082	$231.71	$231.70	$231.70
Purchase #5	$41.53	5.693%	$43.8943	$43.89	$43.90	$43.90
Purchase #6	$176.89	12.802%	$199.5355	$199.54	$199.55	$199.50
Purchase #7	$63.80	13.642%	$72.5036	$72.50	$72.50	$72.50
7 purchase totals =	$817.86		$889.5645	$889.56	$889.55	$889.50