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	$237.32	8.193%	$256.7636	$256.76	$256.75	$256.80
Purchase #2	$78.70	6.112%	$83.5101	$83.51	$83.50	$83.50
Purchase #3	$196.46	7.307%	$210.8153	$210.82	$210.80	$210.80
Purchase #4	$77.84	4.658%	$81.4658	$81.47	$81.45	$81.50
Purchase #5	$113.50	3.196%	$117.1275	$117.13	$117.15	$117.10
Purchase #6	$81.85	5.646%	$86.4713	$86.47	$86.45	$86.50
Purchase #7	$135.35	7.349%	$145.2969	$145.30	$145.30	$145.30
7 purchase totals =	$921.02		$981.4505	$981.46	$981.40	$981.50