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	$7.31	4.433%	$7.6341	$7.63	$7.65	$7.60
Purchase #2	$117.50	9.445%	$128.5979	$128.60	$128.60	$128.60
Purchase #3	$202.63	10.821%	$224.5566	$224.56	$224.55	$224.60
Purchase #4	$11.86	7.208%	$12.7149	$12.71	$12.70	$12.70
Purchase #5	$29.97	8.457%	$32.5046	$32.50	$32.50	$32.50
Purchase #6	$120.56	13.736%	$137.1201	$137.12	$137.10	$137.10
Purchase #7	$215.57	10.628%	$238.4808	$238.48	$238.50	$238.50
7 purchase totals =	$705.40		$781.6090	$781.60	$781.60	$781.60