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 $47.56   3.546%   $49.2465   $49.25   $49.25   $49.20  
  Purchase #2 $222.83   6.107%   $236.4382   $236.44   $236.45   $236.40  
  Purchase #3 $161.29   5.503%   $170.1658   $170.17   $170.15   $170.20  
  Purchase #4 $148.62   5.864%   $157.3351   $157.34   $157.35   $157.30  
  Purchase #5 $136.40   9.421%   $149.2502   $149.25   $149.25   $149.30  
  Purchase #6 $140.40   13.377%   $159.1813   $159.18   $159.20   $159.20  
  Purchase #7 $186.64   8.119%   $201.7933   $201.79   $201.80   $201.80  
  7 purchase totals = $1,043.74       $1,123.4104   $1,123.42   $1,123.45   $1,123.40