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	$31.85	11.502%	$35.5134	$35.51	$35.50	$35.50
Purchase #2	$118.81	7.261%	$127.4368	$127.44	$127.45	$127.40
Purchase #3	$204.50	4.509%	$213.7209	$213.72	$213.70	$213.70
Purchase #4	$218.69	7.606%	$235.3236	$235.32	$235.30	$235.30
Purchase #5	$95.36	6.769%	$101.8149	$101.81	$101.80	$101.80
Purchase #6	$9.64	3.779%	$10.0043	$10.00	$10.00	$10.00
Purchase #7	$31.28	13.780%	$35.5904	$35.59	$35.60	$35.60
7 purchase totals =	$710.13		$759.4043	$759.39	$759.35	$759.30