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	$40.96	13.217%	$46.3737	$46.37	$46.35	$46.40
Purchase #2	$224.30	5.336%	$236.2686	$236.27	$236.25	$236.30
Purchase #3	$231.52	6.451%	$246.4554	$246.46	$246.45	$246.50
Purchase #4	$47.94	10.506%	$52.9766	$52.98	$53.00	$53.00
Purchase #5	$77.45	10.737%	$85.7658	$85.77	$85.75	$85.80
Purchase #6	$166.43	11.652%	$185.8224	$185.82	$185.80	$185.80
Purchase #7	$94.80	4.437%	$99.0063	$99.01	$99.00	$99.00
7 purchase totals =	$883.40		$952.6688	$952.68	$952.60	$952.80