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	$229.54	11.475%	$255.8797	$255.88	$255.90	$255.90
Purchase #2	$149.36	6.119%	$158.4993	$158.50	$158.50	$158.50
Purchase #3	$158.62	9.213%	$173.2337	$173.23	$173.25	$173.20
Purchase #4	$55.98	5.856%	$59.2582	$59.26	$59.25	$59.30
Purchase #5	$48.38	3.724%	$50.1817	$50.18	$50.20	$50.20
Purchase #6	$73.30	7.361%	$78.6956	$78.70	$78.70	$78.70
Purchase #7	$219.78	12.357%	$246.9382	$246.94	$246.95	$246.90
7 purchase totals =	$934.96		$1,022.6864	$1,022.69	$1,022.75	$1,022.70