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	$59.89	4.670%	$62.6869	$62.69	$62.70	$62.70
Purchase #2	$249.94	8.586%	$271.3998	$271.40	$271.40	$271.40
Purchase #3	$111.84	12.725%	$126.0716	$126.07	$126.05	$126.10
Purchase #4	$35.29	13.293%	$39.9811	$39.98	$40.00	$40.00
Purchase #5	$38.29	11.286%	$42.6114	$42.61	$42.60	$42.60
Purchase #6	$92.49	12.682%	$104.2196	$104.22	$104.20	$104.20
Purchase #7	$183.95	3.495%	$190.3791	$190.38	$190.40	$190.40
7 purchase totals =	$771.69		$837.3495	$837.35	$837.35	$837.40