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 $210.81   10.160%   $232.2283   $232.23   $232.25   $232.20  
  Purchase #2 $208.81   12.170%   $234.2222   $234.22   $234.20   $234.20  
  Purchase #3 $86.72   7.393%   $93.1312   $93.13   $93.15   $93.10  
  Purchase #4 $151.70   6.661%   $161.8047   $161.80   $161.80   $161.80  
  Purchase #5 $56.43   10.279%   $62.2304   $62.23   $62.25   $62.20  
  Purchase #6 $230.91   12.182%   $259.0395   $259.04   $259.05   $259.00  
  Purchase #7 $67.48   12.593%   $75.9778   $75.98   $76.00   $76.00  
  7 purchase totals = $1,012.86       $1,118.6341   $1,118.63   $1,118.70   $1,118.50