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 $57.53   4.462%   $60.097   $60.10   $60.10   $60.10  
  Purchase #2 $214.63   5.640%   $226.7351   $226.74   $226.75   $226.70  
  Purchase #3 $93.93   4.853%   $98.4884   $98.49   $98.50   $98.50  
  Purchase #4 $236.70   8.541%   $256.9165   $256.92   $256.90   $256.90  
  Purchase #5 $65.39   5.313%   $68.8642   $68.86   $68.85   $68.90  
  Purchase #6 $246.42   4.768%   $258.1693   $258.17   $258.15   $258.20  
  Purchase #7 $162.32   12.328%   $182.3308   $182.33   $182.35   $182.30  
  7 purchase totals = $1,076.92       $1,151.6013   $1,151.61   $1,151.60   $1,151.60