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	$93.66	7.352%	$100.5459	$100.55	$100.55	$100.50
Purchase #2	$114.62	4.218%	$119.4547	$119.45	$119.45	$119.50
Purchase #3	$43.48	3.458%	$44.9835	$44.98	$45.00	$45.00
Purchase #4	$202.33	12.197%	$227.0082	$227.01	$227.00	$227.00
Purchase #5	$118.61	4.366%	$123.7885	$123.79	$123.80	$123.80
Purchase #6	$120.41	5.168%	$126.6328	$126.63	$126.65	$126.60
Purchase #7	$127.59	9.797%	$140.09	$140.09	$140.10	$140.10
7 purchase totals =	$820.70		$882.5036	$882.50	$882.55	$882.50