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 $63.95   10.611%   $70.7357   $70.74   $70.75   $70.70  
  Purchase #2 $52.62   10.527%   $58.1593   $58.16   $58.15   $58.20  
  Purchase #3 $213.41   10.393%   $235.5897   $235.59   $235.60   $235.60  
  Purchase #4 $248.48   6.734%   $265.2126   $265.21   $265.20   $265.20  
  Purchase #5 $11.49   12.585%   $12.936   $12.94   $12.95   $12.90  
  Purchase #6 $22.96   13.390%   $26.0343   $26.03   $26.05   $26.00  
  Purchase #7 $249.81   9.585%   $273.7543   $273.75   $273.75   $273.80  
  7 purchase totals = $862.72       $942.4219   $942.42   $942.45   $942.40