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	$199.68	5.595%	$210.8521	$210.85	$210.85	$210.90
Purchase #2	$189.92	12.443%	$213.5517	$213.55	$213.55	$213.60
Purchase #3	$77.62	6.616%	$82.7553	$82.76	$82.75	$82.80
Purchase #4	$57.63	3.492%	$59.6424	$59.64	$59.65	$59.60
Purchase #5	$161.44	10.171%	$177.8601	$177.86	$177.85	$177.90
Purchase #6	$92.55	8.188%	$100.128	$100.13	$100.15	$100.10
Purchase #7	$105.65	4.537%	$110.4433	$110.44	$110.45	$110.40
7 purchase totals =	$884.49		$955.2329	$955.23	$955.25	$955.30