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	$40.46	7.438%	$43.4694	$43.47	$43.45	$43.50
Purchase #2	$54.86	5.766%	$58.0232	$58.02	$58.00	$58.00
Purchase #3	$237.61	7.700%	$255.906	$255.91	$255.90	$255.90
Purchase #4	$178.99	9.468%	$195.9368	$195.94	$195.95	$195.90
Purchase #5	$112.87	6.200%	$119.8679	$119.87	$119.85	$119.90
Purchase #6	$142.77	4.228%	$148.8063	$148.81	$148.80	$148.80
Purchase #7	$180.80	4.808%	$189.4929	$189.49	$189.50	$189.50
7 purchase totals =	$948.36		$1,011.5025	$1,011.51	$1,011.45	$1,011.50