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	$215.44	11.764%	$240.7844	$240.78	$240.80	$240.80
Purchase #2	$160.89	11.423%	$179.2685	$179.27	$179.25	$179.30
Purchase #3	$246.94	7.393%	$265.1963	$265.20	$265.20	$265.20
Purchase #4	$132.85	5.276%	$139.8592	$139.86	$139.85	$139.90
Purchase #5	$185.45	13.581%	$210.636	$210.64	$210.65	$210.60
Purchase #6	$131.34	9.208%	$143.4338	$143.43	$143.45	$143.40
Purchase #7	$29.50	5.322%	$31.07	$31.07	$31.05	$31.10
7 purchase totals =	$1,102.41		$1,210.2482	$1,210.25	$1,210.25	$1,210.30