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	$140.64	9.858%	$154.5043	$154.50	$154.50	$154.50
Purchase #2	$36.27	3.303%	$37.468	$37.47	$37.45	$37.50
Purchase #3	$40.59	5.576%	$42.8533	$42.85	$42.85	$42.90
Purchase #4	$119.25	3.825%	$123.8113	$123.81	$123.80	$123.80
Purchase #5	$243.32	12.531%	$273.8104	$273.81	$273.80	$273.80
Purchase #6	$62.65	12.791%	$70.6636	$70.66	$70.65	$70.70
Purchase #7	$244.66	5.357%	$257.7664	$257.77	$257.75	$257.80
7 purchase totals =	$887.38		$960.8773	$960.87	$960.80	$961.00