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	$232.69	9.689%	$255.2353	$255.24	$255.25	$255.20
Purchase #2	$169.82	3.409%	$175.6092	$175.61	$175.60	$175.60
Purchase #3	$102.58	10.523%	$113.3745	$113.37	$113.35	$113.40
Purchase #4	$123.35	8.423%	$133.7398	$133.74	$133.75	$133.70
Purchase #5	$152.93	11.672%	$170.78	$170.78	$170.80	$170.80
Purchase #6	$56.83	7.648%	$61.1764	$61.18	$61.20	$61.20
Purchase #7	$52.69	4.127%	$54.8645	$54.86	$54.85	$54.90
7 purchase totals =	$890.89		$964.7797	$964.78	$964.80	$964.80