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 $183.66   8.480%   $199.2344   $199.23   $199.25   $199.20  
  Purchase #2 $164.43   13.681%   $186.9257   $186.93   $186.95   $186.90  
  Purchase #3 $154.63   9.774%   $169.7435   $169.74   $169.75   $169.70  
  Purchase #4 $221.86   9.440%   $242.8036   $242.80   $242.80   $242.80  
  Purchase #5 $31.80   5.573%   $33.5722   $33.57   $33.55   $33.60  
  Purchase #6 $239.62   6.218%   $254.5196   $254.52   $254.50   $254.50  
  Purchase #7 $186.26   11.785%   $208.2107   $208.21   $208.20   $208.20  
  7 purchase totals = $1,182.26       $1,295.0097   $1,295.00   $1,295.00   $1,294.90