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	$65.59	11.724%	$73.2798	$73.28	$73.30	$73.30
Purchase #2	$148.59	11.455%	$165.611	$165.61	$165.60	$165.60
Purchase #3	$119.55	4.500%	$124.9298	$124.93	$124.95	$124.90
Purchase #4	$32.82	8.315%	$35.549	$35.55	$35.55	$35.50
Purchase #5	$229.28	12.196%	$257.243	$257.24	$257.25	$257.20
Purchase #6	$244.25	6.241%	$259.4936	$259.49	$259.50	$259.50
Purchase #7	$100.96	7.585%	$108.6178	$108.62	$108.60	$108.60
7 purchase totals =	$941.04		$1,024.7240	$1,024.72	$1,024.75	$1,024.60