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	$233.48	13.587%	$265.2029	$265.20	$265.20	$265.20
Purchase #2	$40.67	5.513%	$42.9121	$42.91	$42.90	$42.90
Purchase #3	$226.67	13.241%	$256.6834	$256.68	$256.70	$256.70
Purchase #4	$16.50	5.359%	$17.3842	$17.38	$17.40	$17.40
Purchase #5	$183.37	12.274%	$205.8768	$205.88	$205.90	$205.90
Purchase #6	$154.27	11.693%	$172.3088	$172.31	$172.30	$172.30
Purchase #7	$108.61	7.230%	$116.4625	$116.46	$116.45	$116.50
7 purchase totals =	$963.57		$1,076.8307	$1,076.82	$1,076.85	$1,076.90