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	$82.48	7.236%	$88.4483	$88.45	$88.45	$88.40
Purchase #2	$34.92	13.158%	$39.5148	$39.51	$39.50	$39.50
Purchase #3	$189.37	13.804%	$215.5106	$215.51	$215.50	$215.50
Purchase #4	$173.79	5.815%	$183.8959	$183.90	$183.90	$183.90
Purchase #5	$180.82	12.546%	$203.5057	$203.51	$203.50	$203.50
Purchase #6	$51.55	4.428%	$53.8326	$53.83	$53.85	$53.80
Purchase #7	$154.51	5.184%	$162.5198	$162.52	$162.50	$162.50
7 purchase totals =	$867.44		$947.2277	$947.23	$947.20	$947.10