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	$242.29	5.498%	$255.6111	$255.61	$255.60	$255.60
Purchase #2	$70.35	8.134%	$76.0723	$76.07	$76.05	$76.10
Purchase #3	$104.88	5.873%	$111.0396	$111.04	$111.05	$111.00
Purchase #4	$240.37	6.460%	$255.8979	$255.90	$255.90	$255.90
Purchase #5	$58.46	7.342%	$62.7521	$62.75	$62.75	$62.80
Purchase #6	$11.68	10.725%	$12.9327	$12.93	$12.95	$12.90
Purchase #7	$176.48	9.113%	$192.5626	$192.56	$192.55	$192.60
7 purchase totals =	$904.51		$966.8683	$966.86	$966.85	$966.90