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	$239.37	9.664%	$262.5027	$262.50	$262.50	$262.50
Purchase #2	$107.31	5.827%	$113.563	$113.56	$113.55	$113.60
Purchase #3	$173.55	8.477%	$188.2618	$188.26	$188.25	$188.30
Purchase #4	$38.50	8.359%	$41.7182	$41.72	$41.70	$41.70
Purchase #5	$69.37	12.317%	$77.9143	$77.91	$77.90	$77.90
Purchase #6	$152.77	7.630%	$164.4264	$164.43	$164.45	$164.40
Purchase #7	$153.25	10.628%	$169.5374	$169.54	$169.55	$169.50
7 purchase totals =	$934.12		$1,017.9238	$1,017.92	$1,017.90	$1,017.90