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 $59.51   4.794%   $62.3629   $62.36   $62.35   $62.40  
  Purchase #2 $226.41   8.449%   $245.5394   $245.54   $245.55   $245.50  
  Purchase #3 $154.86   11.778%   $173.0994   $173.10   $173.10   $173.10  
  Purchase #4 $23.94   9.423%   $26.1959   $26.20   $26.20   $26.20  
  Purchase #5 $245.50   10.709%   $271.7906   $271.79   $271.80   $271.80  
  Purchase #6 $145.49   13.379%   $164.9551   $164.96   $164.95   $165.00  
  Purchase #7 $221.27   5.850%   $234.2143   $234.21   $234.20   $234.20  
  7 purchase totals = $1,076.98       $1,178.1576   $1,178.16   $1,178.15   $1,178.20