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	$218.71	9.200%	$238.8313	$238.83	$238.85	$238.80
Purchase #2	$236.82	8.638%	$257.2765	$257.28	$257.30	$257.30
Purchase #3	$161.89	13.153%	$183.1834	$183.18	$183.20	$183.20
Purchase #4	$43.81	12.633%	$49.3445	$49.34	$49.35	$49.30
Purchase #5	$81.98	10.393%	$90.5002	$90.50	$90.50	$90.50
Purchase #6	$182.79	4.458%	$190.9388	$190.94	$190.95	$190.90
Purchase #7	$157.78	9.349%	$172.5309	$172.53	$172.55	$172.50
7 purchase totals =	$1,083.78		$1,182.6056	$1,182.60	$1,182.70	$1,182.50