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	$87.26	9.411%	$95.472	$95.47	$95.45	$95.50
Purchase #2	$244.91	5.532%	$258.4584	$258.46	$258.45	$258.50
Purchase #3	$127.63	6.609%	$136.0651	$136.07	$136.05	$136.10
Purchase #4	$97.36	5.742%	$102.9504	$102.95	$102.95	$103.00
Purchase #5	$80.72	12.575%	$90.8705	$90.87	$90.85	$90.90
Purchase #6	$74.65	5.507%	$78.761	$78.76	$78.75	$78.80
Purchase #7	$145.49	3.123%	$150.0337	$150.03	$150.05	$150.00
7 purchase totals =	$858.02		$912.6111	$912.61	$912.55	$912.80