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 $189.82   3.661%   $196.7693   $196.77   $196.75   $196.80  
  Purchase #2 $165.85   12.408%   $186.4287   $186.43   $186.45   $186.40  
  Purchase #3 $212.73   3.689%   $220.5776   $220.58   $220.60   $220.60  
  Purchase #4 $234.71   7.654%   $252.6747   $252.67   $252.65   $252.70  
  Purchase #5 $136.42   3.306%   $140.93   $140.93   $140.95   $140.90  
  Purchase #6 $195.70   4.343%   $204.1993   $204.20   $204.20   $204.20  
  Purchase #7 $242.73   7.722%   $261.4736   $261.47   $261.45   $261.50  
  7 purchase totals = $1,377.96       $1,463.0532   $1,463.05   $1,463.05   $1,463.10