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	$215.50	3.442%	$222.9175	$222.92	$222.90	$222.90
Purchase #2	$210.63	10.502%	$232.7504	$232.75	$232.75	$232.80
Purchase #3	$246.96	9.839%	$271.2584	$271.26	$271.25	$271.30
Purchase #4	$105.80	5.420%	$111.5344	$111.53	$111.55	$111.50
Purchase #5	$190.26	12.198%	$213.4679	$213.47	$213.45	$213.50
Purchase #6	$60.80	7.742%	$65.5071	$65.51	$65.50	$65.50
Purchase #7	$64.37	3.423%	$66.5734	$66.57	$66.55	$66.60
7 purchase totals =	$1,094.32		$1,184.0091	$1,184.01	$1,183.95	$1,184.10