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	$85.57	10.667%	$94.6978	$94.70	$94.70	$94.70
Purchase #2	$181.27	4.711%	$189.8096	$189.81	$189.80	$189.80
Purchase #3	$120.98	5.640%	$127.8033	$127.80	$127.80	$127.80
Purchase #4	$41.96	11.156%	$46.6411	$46.64	$46.65	$46.60
Purchase #5	$152.50	12.414%	$171.4314	$171.43	$171.45	$171.40
Purchase #6	$106.39	4.347%	$111.0148	$111.01	$111.00	$111.00
Purchase #7	$155.26	7.387%	$166.7291	$166.73	$166.75	$166.70
7 purchase totals =	$843.93		$908.1271	$908.12	$908.15	$908.00