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 $62.95   9.533%   $68.951   $68.95   $68.95   $69.00  
  Purchase #2 $208.98   3.122%   $215.5044   $215.50   $215.50   $215.50  
  Purchase #3 $20.38   11.645%   $22.7533   $22.75   $22.75   $22.80  
  Purchase #4 $105.91   7.818%   $114.19   $114.19   $114.20   $114.20  
  Purchase #5 $146.62   6.277%   $155.8233   $155.82   $155.80   $155.80  
  Purchase #6 $65.90   8.797%   $71.6972   $71.70   $71.70   $71.70  
  Purchase #7 $231.38   10.551%   $255.7929   $255.79   $255.80   $255.80  
  7 purchase totals = $842.12       $904.7121   $904.70   $904.70   $904.80