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	$228.77	13.151%	$258.8555	$258.86	$258.85	$258.90
Purchase #2	$33.48	5.800%	$35.4218	$35.42	$35.40	$35.40
Purchase #3	$113.65	8.538%	$123.3534	$123.35	$123.35	$123.40
Purchase #4	$62.46	5.457%	$65.8684	$65.87	$65.85	$65.90
Purchase #5	$150.76	13.266%	$170.7598	$170.76	$170.75	$170.80
Purchase #6	$168.51	10.603%	$186.3771	$186.38	$186.40	$186.40
Purchase #7	$168.85	7.448%	$181.4259	$181.43	$181.45	$181.40
7 purchase totals =	$926.48		$1,022.0619	$1,022.07	$1,022.05	$1,022.20