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	$171.95	5.636%	$181.6411	$181.64	$181.65	$181.60
Purchase #2	$244.54	12.843%	$275.9463	$275.95	$275.95	$275.90
Purchase #3	$30.38	3.522%	$31.45	$31.45	$31.45	$31.50
Purchase #4	$78.81	4.789%	$82.5842	$82.58	$82.60	$82.60
Purchase #5	$31.90	11.694%	$35.6304	$35.63	$35.65	$35.60
Purchase #6	$114.53	6.823%	$122.3444	$122.34	$122.35	$122.30
Purchase #7	$233.66	7.644%	$251.521	$251.52	$251.50	$251.50
7 purchase totals =	$905.77		$981.1174	$981.11	$981.15	$981.00