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	$153.45	12.716%	$172.9627	$172.96	$172.95	$173.00
Purchase #2	$34.54	11.487%	$38.5076	$38.51	$38.50	$38.50
Purchase #3	$107.43	11.257%	$119.5234	$119.52	$119.50	$119.50
Purchase #4	$246.73	4.440%	$257.6848	$257.68	$257.70	$257.70
Purchase #5	$187.92	12.285%	$211.006	$211.01	$211.00	$211.00
Purchase #6	$155.39	5.710%	$164.2628	$164.26	$164.25	$164.30
Purchase #7	$72.85	7.411%	$78.2489	$78.25	$78.25	$78.20
7 purchase totals =	$958.31		$1,042.1962	$1,042.19	$1,042.15	$1,042.20