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	$133.84	7.601%	$144.0132	$144.01	$144.00	$144.00
Purchase #2	$142.63	3.344%	$147.3995	$147.40	$147.40	$147.40
Purchase #3	$183.54	8.581%	$199.2896	$199.29	$199.30	$199.30
Purchase #4	$86.79	4.536%	$90.7268	$90.73	$90.75	$90.70
Purchase #5	$166.86	8.515%	$181.0681	$181.07	$181.05	$181.10
Purchase #6	$128.59	11.859%	$143.8395	$143.84	$143.85	$143.80
Purchase #7	$95.67	5.734%	$101.1557	$101.16	$101.15	$101.20
7 purchase totals =	$937.92		$1,007.4924	$1,007.50	$1,007.50	$1,007.50