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	$204.88	10.720%	$226.8431	$226.84	$226.85	$226.80
Purchase #2	$98.47	13.637%	$111.8984	$111.90	$111.90	$111.90
Purchase #3	$182.59	7.462%	$196.2149	$196.21	$196.20	$196.20
Purchase #4	$115.99	13.422%	$131.5582	$131.56	$131.55	$131.60
Purchase #5	$181.52	5.563%	$191.618	$191.62	$191.60	$191.60
Purchase #6	$242.86	9.655%	$266.3081	$266.31	$266.30	$266.30
Purchase #7	$116.83	12.866%	$131.8613	$131.86	$131.85	$131.90
7 purchase totals =	$1,143.14		$1,256.3020	$1,256.30	$1,256.25	$1,256.30