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	$37.62	6.767%	$40.1657	$40.17	$40.15	$40.20
Purchase #2	$174.37	5.617%	$184.1644	$184.16	$184.15	$184.20
Purchase #3	$136.58	5.342%	$143.8761	$143.88	$143.90	$143.90
Purchase #4	$102.32	9.532%	$112.0731	$112.07	$112.05	$112.10
Purchase #5	$126.62	8.756%	$137.7068	$137.71	$137.70	$137.70
Purchase #6	$215.41	3.284%	$222.4841	$222.48	$222.50	$222.50
Purchase #7	$199.43	12.103%	$223.567	$223.57	$223.55	$223.60
7 purchase totals =	$992.35		$1,064.0372	$1,064.04	$1,064.00	$1,064.20