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	$23.93	4.518%	$25.0112	$25.01	$25.00	$25.00
Purchase #2	$173.33	13.493%	$196.7174	$196.72	$196.70	$196.70
Purchase #3	$232.90	11.709%	$260.1703	$260.17	$260.15	$260.20
Purchase #4	$55.91	5.567%	$59.0225	$59.02	$59.00	$59.00
Purchase #5	$158.90	8.631%	$172.6147	$172.61	$172.60	$172.60
Purchase #6	$173.89	9.777%	$190.8912	$190.89	$190.90	$190.90
Purchase #7	$249.80	7.146%	$267.6507	$267.65	$267.65	$267.70
7 purchase totals =	$1,068.66		$1,172.0780	$1,172.07	$1,172.00	$1,172.10