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	$105.33	10.548%	$116.4402	$116.44	$116.45	$116.40
Purchase #2	$51.44	10.870%	$57.0315	$57.03	$57.05	$57.00
Purchase #3	$190.75	5.296%	$200.8521	$200.85	$200.85	$200.90
Purchase #4	$53.63	7.540%	$57.6737	$57.67	$57.65	$57.70
Purchase #5	$156.48	10.231%	$172.4895	$172.49	$172.50	$172.50
Purchase #6	$218.68	12.534%	$246.0894	$246.09	$246.10	$246.10
Purchase #7	$49.59	12.462%	$55.7699	$55.77	$55.75	$55.80
7 purchase totals =	$825.90		$906.3463	$906.34	$906.35	$906.40