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	$89.55	5.403%	$94.3884	$94.39	$94.40	$94.40
Purchase #2	$179.39	11.512%	$200.0414	$200.04	$200.05	$200.00
Purchase #3	$100.65	3.395%	$104.0671	$104.07	$104.05	$104.10
Purchase #4	$125.38	11.273%	$139.5141	$139.51	$139.50	$139.50
Purchase #5	$45.38	5.663%	$47.9499	$47.95	$47.95	$47.90
Purchase #6	$119.70	13.838%	$136.2641	$136.26	$136.25	$136.30
Purchase #7	$241.40	12.484%	$271.5364	$271.54	$271.55	$271.50
7 purchase totals =	$901.45		$993.7614	$993.76	$993.75	$993.70