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 $222.56   5.832%   $235.5397   $235.54   $235.55   $235.50  
  Purchase #2 $62.57   3.362%   $64.6736   $64.67   $64.65   $64.70  
  Purchase #3 $229.27   7.206%   $245.7912   $245.79   $245.80   $245.80  
  Purchase #4 $244.99   5.671%   $258.8834   $258.88   $258.90   $258.90  
  Purchase #5 $65.69   5.534%   $69.3253   $69.33   $69.35   $69.30  
  Purchase #6 $237.63   9.851%   $261.0389   $261.04   $261.05   $261.00  
  Purchase #7 $232.82   7.238%   $249.6715   $249.67   $249.65   $249.70  
  7 purchase totals = $1,295.53       $1,384.9236   $1,384.92   $1,384.95   $1,384.90