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	$132.97	8.725%	$144.5716	$144.57	$144.55	$144.60
Purchase #2	$92.38	11.195%	$102.7219	$102.72	$102.70	$102.70
Purchase #3	$113.72	6.366%	$120.9594	$120.96	$120.95	$121.00
Purchase #4	$184.93	6.270%	$196.5251	$196.53	$196.55	$196.50
Purchase #5	$100.92	13.738%	$114.7844	$114.78	$114.80	$114.80
Purchase #6	$95.89	9.270%	$104.779	$104.78	$104.80	$104.80
Purchase #7	$183.49	4.370%	$191.5085	$191.51	$191.50	$191.50
7 purchase totals =	$904.30		$975.8499	$975.85	$975.85	$975.90