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	$62.46	12.711%	$70.3993	$70.40	$70.40	$70.40
Purchase #2	$176.75	13.225%	$200.1252	$200.13	$200.15	$200.10
Purchase #3	$92.57	4.669%	$96.8921	$96.89	$96.90	$96.90
Purchase #4	$76.75	13.248%	$86.9178	$86.92	$86.90	$86.90
Purchase #5	$42.94	7.867%	$46.3181	$46.32	$46.30	$46.30
Purchase #6	$198.61	3.628%	$205.8156	$205.82	$205.80	$205.80
Purchase #7	$242.28	6.581%	$258.2244	$258.22	$258.20	$258.20
7 purchase totals =	$892.36		$964.6925	$964.70	$964.65	$964.60