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	$126.33	8.530%	$137.1059	$137.11	$137.10	$137.10
Purchase #2	$100.62	4.241%	$104.8873	$104.89	$104.90	$104.90
Purchase #3	$81.79	5.706%	$86.4569	$86.46	$86.45	$86.50
Purchase #4	$37.93	6.606%	$40.4357	$40.44	$40.45	$40.40
Purchase #5	$12.59	10.150%	$13.8679	$13.87	$13.85	$13.90
Purchase #6	$234.29	4.751%	$245.4211	$245.42	$245.40	$245.40
Purchase #7	$134.35	9.286%	$146.8257	$146.83	$146.85	$146.80
7 purchase totals =	$727.90		$775.0005	$775.02	$775.00	$775.00