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 $57.58   7.239%   $61.7482   $61.75   $61.75   $61.70  
  Purchase #2 $235.91   10.748%   $261.2656   $261.27   $261.25   $261.30  
  Purchase #3 $208.39   4.501%   $217.7696   $217.77   $217.75   $217.80  
  Purchase #4 $39.91   10.246%   $43.9992   $44.00   $44.00   $44.00  
  Purchase #5 $111.42   7.611%   $119.9002   $119.90   $119.90   $119.90  
  Purchase #6 $154.35   11.335%   $171.8456   $171.85   $171.85   $171.80  
  Purchase #7 $162.46   8.656%   $176.5225   $176.52   $176.50   $176.50  
  7 purchase totals = $970.02       $1,053.0509   $1,053.06   $1,053.00   $1,053.00