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	$215.75	3.468%	$223.2322	$223.23	$223.25	$223.20
Purchase #2	$11.91	10.170%	$13.1212	$13.12	$13.10	$13.10
Purchase #3	$109.97	7.233%	$117.9241	$117.92	$117.90	$117.90
Purchase #4	$170.66	6.462%	$181.688	$181.69	$181.70	$181.70
Purchase #5	$115.94	6.506%	$123.4831	$123.48	$123.50	$123.50
Purchase #6	$90.29	9.751%	$99.0942	$99.09	$99.10	$99.10
Purchase #7	$132.35	8.830%	$144.0365	$144.04	$144.05	$144.00
7 purchase totals =	$846.87		$902.5793	$902.57	$902.60	$902.50