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 $59.76   5.319%   $62.9386   $62.94   $62.95   $62.90  
  Purchase #2 $242.56   12.761%   $273.5131   $273.51   $273.50   $273.50  
  Purchase #3 $103.63   8.584%   $112.5256   $112.53   $112.55   $112.50  
  Purchase #4 $159.27   13.206%   $180.3032   $180.30   $180.30   $180.30  
  Purchase #5 $216.72   13.213%   $245.3552   $245.36   $245.35   $245.40  
  Purchase #6 $68.40   12.367%   $76.859   $76.86   $76.85   $76.90  
  Purchase #7 $87.59   5.267%   $92.2034   $92.20   $92.20   $92.20  
  7 purchase totals = $937.93       $1,043.6981   $1,043.70   $1,043.70   $1,043.70