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	$67.85	4.712%	$71.0471	$71.05	$71.05	$71.00
Purchase #2	$112.59	6.228%	$119.6021	$119.60	$119.60	$119.60
Purchase #3	$102.77	3.585%	$106.4543	$106.45	$106.45	$106.50
Purchase #4	$102.51	11.399%	$114.1951	$114.20	$114.20	$114.20
Purchase #5	$6.80	4.797%	$7.1262	$7.13	$7.15	$7.10
Purchase #6	$246.59	13.789%	$280.5923	$280.59	$280.60	$280.60
Purchase #7	$119.39	12.752%	$134.6146	$134.61	$134.60	$134.60
7 purchase totals =	$758.50		$833.6317	$833.63	$833.65	$833.60