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	$45.49	4.191%	$47.3965	$47.40	$47.40	$47.40
Purchase #2	$237.77	7.861%	$256.4611	$256.46	$256.45	$256.50
Purchase #3	$200.53	11.681%	$223.9539	$223.95	$223.95	$224.00
Purchase #4	$137.66	4.676%	$144.097	$144.10	$144.10	$144.10
Purchase #5	$96.85	5.574%	$102.2484	$102.25	$102.25	$102.20
Purchase #6	$208.48	10.543%	$230.46	$230.46	$230.45	$230.50
Purchase #7	$198.65	3.439%	$205.4816	$205.48	$205.50	$205.50
7 purchase totals =	$1,125.43		$1,210.0985	$1,210.10	$1,210.10	$1,210.20