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	$13.60	3.567%	$14.0851	$14.09	$14.10	$14.10
Purchase #2	$223.32	9.239%	$243.9525	$243.95	$243.95	$244.00
Purchase #3	$39.77	7.302%	$42.674	$42.67	$42.65	$42.70
Purchase #4	$91.94	3.379%	$95.0467	$95.05	$95.05	$95.00
Purchase #5	$132.49	6.689%	$141.3523	$141.35	$141.35	$141.40
Purchase #6	$186.51	5.440%	$196.6561	$196.66	$196.65	$196.70
Purchase #7	$22.83	10.250%	$25.1701	$25.17	$25.15	$25.20
7 purchase totals =	$710.46		$758.9368	$758.94	$758.90	$759.10