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 $62.33   12.235%   $69.9561   $69.96   $69.95   $70.00  
  Purchase #2 $179.67   11.175%   $199.7481   $199.75   $199.75   $199.70  
  Purchase #3 $132.78   3.346%   $137.2228   $137.22   $137.20   $137.20  
  Purchase #4 $5.45   10.639%   $6.0298   $6.03   $6.05   $6.00  
  Purchase #5 $46.88   6.545%   $49.9483   $49.95   $49.95   $49.90  
  Purchase #6 $72.48   6.550%   $77.2274   $77.23   $77.25   $77.20  
  Purchase #7 $188.39   12.577%   $212.0838   $212.08   $212.10   $212.10  
  7 purchase totals = $687.98       $752.2163   $752.22   $752.25   $752.10