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 $90.88   4.575%   $95.0378   $95.04   $95.05   $95.00  
  Purchase #2 $230.63   5.794%   $243.9927   $243.99   $244.00   $244.00  
  Purchase #3 $245.90   6.821%   $262.6728   $262.67   $262.65   $262.70  
  Purchase #4 $9.56   9.259%   $10.4452   $10.45   $10.45   $10.40  
  Purchase #5 $41.37   5.597%   $43.6855   $43.69   $43.70   $43.70  
  Purchase #6 $50.50   8.372%   $54.7279   $54.73   $54.75   $54.70  
  Purchase #7 $141.75   7.843%   $152.8675   $152.87   $152.85   $152.90  
  7 purchase totals = $810.59       $863.4294   $863.44   $863.45   $863.40