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	$10.75	9.105%	$11.7288	$11.73	$11.75	$11.70
Purchase #2	$76.69	12.810%	$86.514	$86.51	$86.50	$86.50
Purchase #3	$159.39	8.542%	$173.0051	$173.01	$173.00	$173.00
Purchase #4	$54.35	9.839%	$59.6975	$59.70	$59.70	$59.70
Purchase #5	$34.57	3.822%	$35.8913	$35.89	$35.90	$35.90
Purchase #6	$113.48	5.202%	$119.3832	$119.38	$119.40	$119.40
Purchase #7	$35.30	12.277%	$39.6338	$39.63	$39.65	$39.60
7 purchase totals =	$484.53		$525.8537	$525.85	$525.90	$525.80