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	$217.28	11.547%	$242.3693	$242.37	$242.35	$242.40
Purchase #2	$61.33	12.195%	$68.8092	$68.81	$68.80	$68.80
Purchase #3	$184.50	3.107%	$190.2324	$190.23	$190.25	$190.20
Purchase #4	$216.88	10.409%	$239.455	$239.46	$239.45	$239.50
Purchase #5	$55.33	3.293%	$57.152	$57.15	$57.15	$57.20
Purchase #6	$191.63	12.586%	$215.7486	$215.75	$215.75	$215.70
Purchase #7	$162.70	12.530%	$183.0863	$183.09	$183.10	$183.10
7 purchase totals =	$1,089.65		$1,196.8528	$1,196.86	$1,196.85	$1,196.90