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 $82.73   6.387%   $88.014   $88.01   $88.00   $88.00  
  Purchase #2 $210.61   6.870%   $225.0789   $225.08   $225.10   $225.10  
  Purchase #3 $97.38   5.385%   $102.6239   $102.62   $102.60   $102.60  
  Purchase #4 $122.46   13.352%   $138.8109   $138.81   $138.80   $138.80  
  Purchase #5 $173.46   13.129%   $196.2336   $196.23   $196.25   $196.20  
  Purchase #6 $241.25   9.832%   $264.9697   $264.97   $264.95   $265.00  
  Purchase #7 $227.25   6.735%   $242.5553   $242.56   $242.55   $242.60  
  7 purchase totals = $1,155.14       $1,258.2863   $1,258.28   $1,258.25   $1,258.30