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	$237.66	3.353%	$245.6287	$245.63	$245.65	$245.60
Purchase #2	$127.80	4.864%	$134.0162	$134.02	$134.00	$134.00
Purchase #3	$137.31	4.521%	$143.5178	$143.52	$143.50	$143.50
Purchase #4	$222.87	11.281%	$248.012	$248.01	$248.00	$248.00
Purchase #5	$19.32	10.268%	$21.3038	$21.30	$21.30	$21.30
Purchase #6	$128.86	8.277%	$139.5257	$139.53	$139.55	$139.50
Purchase #7	$139.59	10.612%	$154.4033	$154.40	$154.40	$154.40
7 purchase totals =	$1,013.41		$1,086.4075	$1,086.41	$1,086.40	$1,086.30