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	$174.67	13.298%	$197.8976	$197.90	$197.90	$197.90
Purchase #2	$18.60	9.678%	$20.4001	$20.40	$20.40	$20.40
Purchase #3	$120.73	11.166%	$134.2107	$134.21	$134.20	$134.20
Purchase #4	$127.90	13.402%	$145.0412	$145.04	$145.05	$145.00
Purchase #5	$158.89	8.837%	$172.9311	$172.93	$172.95	$172.90
Purchase #6	$116.77	5.717%	$123.4457	$123.45	$123.45	$123.40
Purchase #7	$138.94	13.359%	$157.501	$157.50	$157.50	$157.50
7 purchase totals =	$856.50		$951.4274	$951.43	$951.45	$951.30