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	$178.45	6.480%	$190.0136	$190.01	$190.00	$190.00
Purchase #2	$128.57	10.669%	$142.2871	$142.29	$142.30	$142.30
Purchase #3	$71.36	6.754%	$76.1797	$76.18	$76.20	$76.20
Purchase #4	$204.86	3.257%	$211.5323	$211.53	$211.55	$211.50
Purchase #5	$159.84	8.358%	$173.1994	$173.20	$173.20	$173.20
Purchase #6	$80.49	6.165%	$85.4522	$85.45	$85.45	$85.50
Purchase #7	$173.45	13.514%	$196.89	$196.89	$196.90	$196.90
7 purchase totals =	$997.02		$1,075.5543	$1,075.55	$1,075.60	$1,075.60