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	$131.82	9.618%	$144.4984	$144.50	$144.50	$144.50
Purchase #2	$182.64	9.389%	$199.7881	$199.79	$199.80	$199.80
Purchase #3	$45.47	12.462%	$51.1365	$51.14	$51.15	$51.10
Purchase #4	$31.38	4.574%	$32.8153	$32.82	$32.80	$32.80
Purchase #5	$21.45	4.316%	$22.3758	$22.38	$22.40	$22.40
Purchase #6	$238.75	12.788%	$269.2814	$269.28	$269.30	$269.30
Purchase #7	$50.48	6.412%	$53.7168	$53.72	$53.70	$53.70
7 purchase totals =	$701.99		$773.6123	$773.63	$773.65	$773.60