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 $60.76   7.712%   $65.4458   $65.45   $65.45   $65.40  
  Purchase #2 $159.77   4.175%   $166.4404   $166.44   $166.45   $166.40  
  Purchase #3 $197.98   4.597%   $207.0811   $207.08   $207.10   $207.10  
  Purchase #4 $149.31   3.138%   $153.9953   $154.00   $154.00   $154.00  
  Purchase #5 $60.35   10.143%   $66.4713   $66.47   $66.45   $66.50  
  Purchase #6 $154.46   8.462%   $167.5304   $167.53   $167.55   $167.50  
  Purchase #7 $184.39   7.684%   $198.5585   $198.56   $198.55   $198.60  
  7 purchase totals = $967.02       $1,025.5228   $1,025.53   $1,025.55   $1,025.50