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	$36.92	13.371%	$41.8566	$41.86	$41.85	$41.90
Purchase #2	$163.82	10.706%	$181.3586	$181.36	$181.35	$181.40
Purchase #3	$186.33	5.109%	$195.8496	$195.85	$195.85	$195.80
Purchase #4	$157.88	4.671%	$165.2546	$165.25	$165.25	$165.30
Purchase #5	$199.95	8.324%	$216.5938	$216.59	$216.60	$216.60
Purchase #6	$34.56	11.305%	$38.467	$38.47	$38.45	$38.50
Purchase #7	$162.78	8.686%	$176.9191	$176.92	$176.90	$176.90
7 purchase totals =	$942.24		$1,016.2993	$1,016.30	$1,016.25	$1,016.40