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	$75.43	10.125%	$83.0673	$83.07	$83.05	$83.10
Purchase #2	$161.58	3.723%	$167.5956	$167.60	$167.60	$167.60
Purchase #3	$116.34	5.730%	$123.0063	$123.01	$123.00	$123.00
Purchase #4	$122.99	6.161%	$130.5674	$130.57	$130.55	$130.60
Purchase #5	$197.45	5.666%	$208.6375	$208.64	$208.65	$208.60
Purchase #6	$231.85	11.758%	$259.1109	$259.11	$259.10	$259.10
Purchase #7	$126.82	8.696%	$137.8483	$137.85	$137.85	$137.80
7 purchase totals =	$1,032.46		$1,109.8333	$1,109.85	$1,109.80	$1,109.80