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	$126.93	10.216%	$139.8972	$139.90	$139.90	$139.90
Purchase #2	$161.58	13.165%	$182.852	$182.85	$182.85	$182.90
Purchase #3	$215.86	4.671%	$225.9428	$225.94	$225.95	$225.90
Purchase #4	$181.71	3.778%	$188.575	$188.58	$188.60	$188.60
Purchase #5	$84.52	6.845%	$90.3054	$90.31	$90.30	$90.30
Purchase #6	$186.87	13.618%	$212.318	$212.32	$212.30	$212.30
Purchase #7	$33.60	7.491%	$36.117	$36.12	$36.10	$36.10
7 purchase totals =	$991.07		$1,076.0074	$1,076.02	$1,076.00	$1,076.00