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	$137.87	11.707%	$154.0104	$154.01	$154.00	$154.00
Purchase #2	$217.35	4.109%	$226.2809	$226.28	$226.30	$226.30
Purchase #3	$109.54	12.474%	$123.204	$123.20	$123.20	$123.20
Purchase #4	$103.63	9.842%	$113.8293	$113.83	$113.85	$113.80
Purchase #5	$20.71	3.179%	$21.3684	$21.37	$21.35	$21.40
Purchase #6	$242.40	7.591%	$260.8006	$260.80	$260.80	$260.80
Purchase #7	$36.96	9.611%	$40.5122	$40.51	$40.50	$40.50
7 purchase totals =	$868.46		$940.0058	$940.00	$940.00	$940.00