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	$206.25	9.297%	$225.4251	$225.43	$225.45	$225.40
Purchase #2	$86.67	9.314%	$94.7424	$94.74	$94.75	$94.70
Purchase #3	$187.85	4.537%	$196.3728	$196.37	$196.35	$196.40
Purchase #4	$175.73	3.598%	$182.0528	$182.05	$182.05	$182.10
Purchase #5	$65.36	10.167%	$72.0052	$72.01	$72.00	$72.00
Purchase #6	$91.80	6.128%	$97.4255	$97.43	$97.45	$97.40
Purchase #7	$99.86	12.748%	$112.5902	$112.59	$112.60	$112.60
7 purchase totals =	$913.52		$980.6140	$980.62	$980.65	$980.60