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	$119.94	9.708%	$131.5838	$131.58	$131.60	$131.60
Purchase #2	$192.89	6.740%	$205.8908	$205.89	$205.90	$205.90
Purchase #3	$136.51	13.862%	$155.433	$155.43	$155.45	$155.40
Purchase #4	$30.49	3.382%	$31.5212	$31.52	$31.50	$31.50
Purchase #5	$75.28	10.762%	$83.3816	$83.38	$83.40	$83.40
Purchase #6	$67.36	6.612%	$71.8138	$71.81	$71.80	$71.80
Purchase #7	$164.73	12.322%	$185.028	$185.03	$185.05	$185.00
7 purchase totals =	$787.20		$864.6522	$864.64	$864.70	$864.60