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	$196.94	9.620%	$215.8856	$215.89	$215.90	$215.90
Purchase #2	$38.77	7.745%	$41.7727	$41.77	$41.75	$41.80
Purchase #3	$92.46	9.231%	$100.995	$101.00	$101.00	$101.00
Purchase #4	$224.50	8.716%	$244.0674	$244.07	$244.05	$244.10
Purchase #5	$70.59	3.184%	$72.8376	$72.84	$72.85	$72.80
Purchase #6	$66.91	6.457%	$71.2304	$71.23	$71.25	$71.20
Purchase #7	$128.90	6.438%	$137.1986	$137.20	$137.20	$137.20
7 purchase totals =	$819.07		$883.9873	$884.00	$884.00	$884.00