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	$54.30	10.202%	$59.8397	$59.84	$59.85	$59.80
Purchase #2	$106.91	11.358%	$119.0528	$119.05	$119.05	$119.10
Purchase #3	$19.54	12.102%	$21.9047	$21.90	$21.90	$21.90
Purchase #4	$29.39	11.580%	$32.7934	$32.79	$32.80	$32.80
Purchase #5	$116.38	12.859%	$131.3453	$131.35	$131.35	$131.30
Purchase #6	$16.46	11.645%	$18.3768	$18.38	$18.40	$18.40
Purchase #7	$163.37	10.569%	$180.6366	$180.64	$180.65	$180.60
7 purchase totals =	$506.35		$563.9493	$563.95	$564.00	$563.90