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	$183.55	8.345%	$198.8672	$198.87	$198.85	$198.90
Purchase #2	$48.29	4.843%	$50.6287	$50.63	$50.65	$50.60
Purchase #3	$34.38	10.707%	$38.0611	$38.06	$38.05	$38.10
Purchase #4	$226.63	13.123%	$256.3707	$256.37	$256.35	$256.40
Purchase #5	$97.28	7.709%	$104.7793	$104.78	$104.80	$104.80
Purchase #6	$88.90	12.861%	$100.3334	$100.33	$100.35	$100.30
Purchase #7	$194.87	10.828%	$215.9705	$215.97	$215.95	$216.00
7 purchase totals =	$873.90		$965.0109	$965.01	$965.00	$965.10