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	$192.84	8.172%	$208.5989	$208.60	$208.60	$208.60
Purchase #2	$35.28	9.334%	$38.573	$38.57	$38.55	$38.60
Purchase #3	$94.55	13.446%	$107.2632	$107.26	$107.25	$107.30
Purchase #4	$189.76	12.298%	$213.0967	$213.10	$213.10	$213.10
Purchase #5	$117.51	8.480%	$127.4748	$127.47	$127.45	$127.50
Purchase #6	$92.88	8.151%	$100.4506	$100.45	$100.45	$100.50
Purchase #7	$24.33	6.374%	$25.8808	$25.88	$25.90	$25.90
7 purchase totals =	$747.15		$821.3380	$821.33	$821.30	$821.50