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	$213.58	5.156%	$224.5922	$224.59	$224.60	$224.60
Purchase #2	$121.49	8.590%	$131.926	$131.93	$131.95	$131.90
Purchase #3	$181.59	8.264%	$196.5966	$196.60	$196.60	$196.60
Purchase #4	$47.78	9.650%	$52.3908	$52.39	$52.40	$52.40
Purchase #5	$115.76	9.281%	$126.5037	$126.50	$126.50	$126.50
Purchase #6	$164.73	11.571%	$183.7909	$183.79	$183.80	$183.80
Purchase #7	$219.53	10.241%	$242.0121	$242.01	$242.00	$242.00
7 purchase totals =	$1,064.46		$1,157.8123	$1,157.81	$1,157.85	$1,157.80