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	$206.97	3.162%	$213.5144	$213.51	$213.50	$213.50
Purchase #2	$96.33	4.581%	$100.7429	$100.74	$100.75	$100.70
Purchase #3	$33.66	10.708%	$37.2643	$37.26	$37.25	$37.30
Purchase #4	$184.84	3.314%	$190.9656	$190.97	$190.95	$191.00
Purchase #5	$7.31	3.708%	$7.5811	$7.58	$7.60	$7.60
Purchase #6	$220.57	6.189%	$234.2211	$234.22	$234.20	$234.20
Purchase #7	$78.85	5.193%	$82.9447	$82.94	$82.95	$82.90
7 purchase totals =	$828.53		$867.2341	$867.22	$867.20	$867.20