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	$233.58	9.349%	$255.4174	$255.42	$255.40	$255.40
Purchase #2	$161.47	8.245%	$174.7832	$174.78	$174.80	$174.80
Purchase #3	$65.98	9.449%	$72.2145	$72.21	$72.20	$72.20
Purchase #4	$13.37	8.815%	$14.5486	$14.55	$14.55	$14.50
Purchase #5	$161.93	10.798%	$179.4152	$179.42	$179.40	$179.40
Purchase #6	$161.61	13.705%	$183.7587	$183.76	$183.75	$183.80
Purchase #7	$211.82	9.176%	$231.2566	$231.26	$231.25	$231.30
7 purchase totals =	$1,009.76		$1,111.3942	$1,111.40	$1,111.35	$1,111.40