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 $218.46   6.638%   $232.9614   $232.96   $232.95   $233.00  
  Purchase #2 $200.26   11.334%   $222.9575   $222.96   $222.95   $223.00  
  Purchase #3 $50.71   5.804%   $53.6532   $53.65   $53.65   $53.70  
  Purchase #4 $154.63   6.350%   $164.449   $164.45   $164.45   $164.40  
  Purchase #5 $234.87   6.297%   $249.6598   $249.66   $249.65   $249.70  
  Purchase #6 $123.72   9.172%   $135.0676   $135.07   $135.05   $135.10  
  Purchase #7 $43.70   10.239%   $48.1744   $48.17   $48.15   $48.20  
  7 purchase totals = $1,026.35       $1,106.9229   $1,106.92   $1,106.85   $1,107.10