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	$243.75	8.329%	$264.0519	$264.05	$264.05	$264.10
Purchase #2	$95.83	4.402%	$100.0484	$100.05	$100.05	$100.00
Purchase #3	$178.47	10.111%	$196.5151	$196.52	$196.50	$196.50
Purchase #4	$88.79	13.849%	$101.0865	$101.09	$101.10	$101.10
Purchase #5	$125.82	9.699%	$138.0233	$138.02	$138.00	$138.00
Purchase #6	$203.64	7.372%	$218.6523	$218.65	$218.65	$218.70
Purchase #7	$217.51	11.495%	$242.5128	$242.51	$242.50	$242.50
7 purchase totals =	$1,153.81		$1,260.8903	$1,260.89	$1,260.85	$1,260.90